This document provides guidelines for designing user
agents that lower barriers to Web accessibility for people with
disabilities (visual, hearing, physical, cognitive, and neurological). User
agents include HTML browsers and other types of software that retrieve and
render Web content. A user agent that conforms to these guidelines will promote accessibility
through its own user interface and through other internal facilities, including
its ability to communicate with other technologies (especially assistive technologies).
Furthermore, all users, not just users with disabilities, are expected to find
conforming user agents to be more usable.

In addition to helping developers of HTML browsers, media players, etc.,
this document will also benefit developers of assistive technologies because it
explains what types of information and control an assistive technology may
expect from a conforming user agent. Technologies not addressed directly by
this document (e.g., technologies for braille rendering) will be essential to
ensuring Web access for some users with disabilities.

This section describes the status of this document at the time of its
publication. Other documents may supersede this document. The latest status of
this document series is maintained at the W3C.

This is the 21 August 2002 Last Call Working Draft of "User Agent
Accessibility Guidelines 1.0". The last call review period ends 18 September
2002. Last Call Working Draft status is described in section
5.2.2 of the Process Document. Since the previous Candidate Recommendation
draft, the UAWG has gathered implementation experience and clarified the
document based on in-depth discussions with user agent and assistive technology
developers.

As a result of the second Candidate Recommendation period, the UAWG:

deleted or modified some checkpoint provisions with low implementation
experience;

retained some checkpoints despite low implementation experience;

added one checkpoint regarding API access to some rendering
information.

The chapter on conformance has also been greatly simplified since the
Candidate Recommendation. The complete list of changes is
available on the Web.

In this review, the User Agent Accessibility Guidelines Working Group is
primarily interested in comments on changes since the Candidate Recommendation.
The Working Group does not expect to make substantial changes to this document
as the result of this review; the document has already received substantial
technical review. The UAWG does expect to make clarifications and to record
issues to be addressed after UAAG 1.0.

Publication as a Working Draft does not imply endorsement by the W3C
Membership. This is a draft document and may be updated, replaced or obsoleted
by other documents at any time. It is inappropriate to cite this document as
other than "work in progress."

Note: With a user agent that implements HTML 4 [HTML4] access
keys, readers may navigate directly to the table of contents via the "c"
character. Users may have to use additional keyboard strokes depending on their
operating environment.

This document specifies requirements that, if satisfied by user agent developers, will lower barriers
to accessibility. This document includes:

This introduction, which provides context for understanding the
requirements listed in section 2.

Section 2 explains twelve general principles of
accessible design, called "guidelines". Each guideline consists of a list of
requirements, called "checkpoints", which must be satisfied in order to conform
to this document.

Section 3 explains how to make claims that
software components satisfy the requirements of section 2.

An appendix offers a summary of this document's principal goals and
structure [UAAG10-SUMMARY].

A second appendix lists all the checkpoints for convenient reference (e.g.,
as a tool for developers to evaluate software for conformance)
[UAAG10-CHECKLIST].

A separate document, entitled "Techniques for User Agent Accessibility
Guidelines 1.0" (the "Techniques document" from here on)
[UAAG10-TECHS], provides suggestions and examples of how each
checkpoint might be satisfied. It also includes references to other
accessibility resources (such as platform-specific software accessibility
guidelines) that provide additional information on how a user agent may satisfy
each checkpoint. The techniques in the Techniques document are informative examples only, and other
strategies may be used or required to satisfy the checkpoints. The Techniques
document is expected to be updated more frequently than the current guidelines.
Developers, W3C Working Groups, users, and others are encouraged to contribute
techniques.

"User Agent Accessibility Guidelines 1.0" (UAAG 1.0) is
part of a series of accessibility guidelines published by the Web Accessibility Initiative (WAI). The documents in this
series reflect an accessibility model in which Web content authors, format
designers, and software developers have roles in ensuring that users with
disabilities have access to the Web. The accessibility-related interests of
these stakeholders intersect and complement each other as follows:

Designers of formats (e.g., HTML, XHTML, XML, SVG, SMIL, MathML, etc.) and
protocols (e.g., HTTP) create specifications that allow communication on the
Web. Format designers include features in these specifications that authors
should use to create accessible content and that user agents should support
through an accessible user interface. The "XML Accessibility Guidelines
(XAG)" [XAG10] explains the
responsibilities of XML format designers; many XAG requirements make sense for
non-XML formats as well.

Authors make use of the accessibility features of different format
specifications, use markup appropriately, write in clear and simple language,
organize a Web site consistently, etc. The "Web Content Accessibility
Guidelines 1.0"
[WCAG10] explains the responsibilities of authors in meeting the
needs of users with disabilities. The "Web Content Accessibility Guidelines
(WCAG) 1.0" is considered the reference for what defines
accessible Web content. The "Authoring Tool Accessibility Guidelines 1.0"
[ATAG10] explains the responsibilities of authoring tool developers.
An accessible authoring tool facilitates the creation of accessible Web content
and may be operated by users with disabilities.

User agent developers design software that meets the needs of users with
disabilities through conformance to other specifications, an accessible user
interface, accessible documentation, and communication with other software
(notably assistive
technologies).

The requirements of this document interact with those of the "Web Content
Accessibility Guidelines 1.0" [WCAG10] in a number of ways:

UAAG 1.0
checkpoint 8.1 requires implementation of the
accessibility features of specifications. Features are those identified as such
and those that satisfy all of the requirements of WCAG 1.0 [WCAG10].

UAAG 1.0 also incorporates some terms and concepts from WCAG 1.0, a
consequence of fact that the documents were designed to complement one
another.

Some requirements of this document take into account limitations of formats,
authors, and designers. Formats generally do not enable authors to encode all
of their knowledge in a way that a user agent can
recognize 100%. A format may lack features required for accessibility. An
author may not make use of the accessibility features of a format or may misuse
a format (which can cause problems for user agents). A user agent designer may
not implement a format specification correctly or completely.

Some of these limitations are taken into account as follows:

UAAG 1.0 includes requirements to satisfy the expectations set by WCAG 1.0
"until user agent" clauses. These clauses make additional requirements of
authors in order to compensate for some limitations of deployed user
agents.

UAAG 1.0 includes several
repair requirements (e.g., checkpoints checkpoint 2.7 and checkpoint 2.10) for
cases where content does not conform to WCAG 1.0. Furthermore, this document
includes some requirements to address certain widespread authoring practices
that are discouraged because they may cause accessibility or usability problems
(e.g., some uses of HTML frames).

Except for the indicated repair checkpoints, UAAG 1.0 only requires user
agents to handle what may be recognized through protocols
and formats. For example, user agents are not expected to recognize that the
author has used "clear and simple" language to express ideas (WCAG 1.0,
checkpoint 14.1). See the section on checkpoint
applicability for more information about what the user agent is expected to
recognize.

The Web Accessibility Initiative
provides other resources and
educational materials to promote Web accessibility. Resources include
information about accessibility policies, links to translations of WAI
materials into languages other than English, information about specialized user
agents and other tools, accessibility training resources, and more.

Note: The Web Accessibility Initiative is developing new
versions of both the Web Content Accessibility Guidelines and the Authoring
Tool Accessibility Guidelines. UAAG 1.0 refers only to the WCAG 1.0 and ATAG
1.0 Recommendations, which will remain available and unchanged.

This document was designed specifically to improve the accessibility of user
agents with multimedia capabilities running in the following type of
environment (typically that of a desktop computer):

The operating environment includes a keyboard (or keyboard
equivalent);

Assistive technologies may be used in the operating environment and may
communicate with the conforming user agent;

The target user agent is one designed for the general public to handle
general-purpose content in ordinary operating conditions.

This document is not designed so that user agents on other types of
platforms (e.g., handheld devices, kiosks, etc.) will readily conform. This
document does not forbid conformance by any user agent, but some
requirements (e.g., implementation of certain application programming
interfaces, or APIs) are not
likely to be satisfied on environments other than the target environment.
Future work by the UAWG may address the accessibility of
user agents running on handheld devices, etc.

Technologies not addressed directly by this document (e.g., those for
braille rendering) will be essential to ensuring Web access for some users with
disabilities. Note that the ability of conforming user agents to communicate
well with assistive technologies will depend in part on the willingness of
assistive technology developers to follow the same standards and conventions
for communication.

In general, a conforming user agent will consist
of several coordinated components, such as a Web browser, a multimedia player,
several plug-ins, features or applications provided by the operating
environment, and documentation distributed with the software or available on
the Web. These components may run on the user's computer or on a server. A
conforming user agent may also include assistive technologies and applications
provided by the operating environment. The current document places no
restrictions on the type or number of components used for conformance.

This does not mean that every component that one has chosen as part of the
user agent has to satisfy every single requirement; some requirements may not
be relevant for a particular component. For instance, if a component does not
have a user interface, it would not be required to satisfy the user interface
requirements. On the other hand, if a component has a user interface, that user
interface would be subject to the requirements of this document. Conformance
addresses the composite user agent as a whole.

To satisfy the requirements of this document, developers are encouraged to
adopt operating environment
conventions and features that benefit accessibility. When an operating
environment feature (e.g., the operating system's audio control panel,
including its user interface) is adopted to satisfy the requirements of this
document, it is part of the user agent.

People with (or without) disabilities access the Web with widely varying
sets of capabilities, software, and hardware. Some users with disabilities:

May not be able to see, hear, move, or speak.

May not be able to perceive, read, or process some types of information
easily or at all.

May not have or be able to use a keyboard or pointing device.

This document does not include requirements to meet all known accessibility
needs. Some known limitations of this document include the following:

Input modalities

This document only includes requirements for keyboard, pointing device, and
voice input modalities. This document includes several checkpoints related to
voice input as part of general input requirements (e.g., the checkpoints of guideline 7 and guideline 11) but does not
otherwise address voice-based navigation or control.

Note: The UAWG intends to coordinate
further work on the topics of voice input and synthesized speech rendering with
groups in W3C's Voice Browser
Activity.

Output modalities

This document does not include requirements for braille rendering. Some
requirements are specific to graphical rendering and others specific to audio
output or synthesized speech output. Speech rendering requirements are made by
checkpoint 4.9 to checkpoint 4.13. Many
of the requirements of this document are generic enough to apply to a variety
of output modalities, including braille. User agents
conform to this document by supporting some combination of graphical and
audio/speech rendering output; see the section on Content type labels for more information.

Size and color of non-text content

This document includes some checkpoints to ensure that the user is able to
control the size and color of visually rendered text content (checkpoints 4.1 and 4.3). This document does
not in general address control of the size and color of visually rendered non-text content.

Note: Resizing capabilities may be required for
conformance to other specifications (e.g., Scalable Vector Graphics [SVG]).

Background image interference

The requirement of checkpoint 3.1 to allow the user to turn off rendering of
background images does not extend to multi-layered rendering.

User control of every user interface component

This document distinguishes user interface features that are part of the user agent user interface
and those that are part of content. Some checkpoints
(e.g., those in guideline 5)
require user control over rendering and behavior that is driven by content only. This document does not always
explicitly require the same control over features of the user agent user
interface. Nevertheless, this document (see checkpoint 7.3) does require user agents to follow software
usability guidelines, which should include requirements for user control over user interface behavior.

Note: It is more difficult for users to distinguish
content from user interface when both are rendered as sound in one temporal dimension, than it is when both are rendered
visually in two spatial dimensions. Thus, developers of user agents that
include audio output or synthesized speech output are encouraged to apply the
requirements of this document to both content and user agent components.

Time parameters

This document includes requirements for control of some time parameters
(including checkpoint 2.4,
checkpoint 4.4, checkpoint 4.5, and checkpoint 4.9). The
requirements are for time parameters that the user agent recognizes and
controls. This document does not include requirements for control of time
parameters managed on the server.

Digital rights management

The User Agent Accessibility Guidelines Working Group recognizes that
further work is necessary in the area of digital rights management as it
relates to accessibility. Digital rights management refers to methods of
describing and perhaps enforcing intellectual property associated with Web
resources.

Note: The User Agent Accessibility Guidelines Working Group
may address these topics in a future version of the User Agent Accessibility
Guidelines. Even though UAAG 1.0 does not address these
topics, user agent developers are encouraged to consider them in their
designs.

One the goals of the authors of this document is to ensure that the
requirements are compatible with other good software design practices. However,
this document does not purport to be a complete guide to good software design.
For instance, the general topic of user interface design for computer software
exceeds the scope of this document, though some user interface requirements
have been included because of their importance to accessibility. The Techniques
document [UAAG10-TECHS] includes some
references to general software design guidelines and platform-specific
accessibility guidelines (see
checkpoint 7.3). Involving people with disabilities in the design and
testing of software will generally improve the accessibility of the
software.

This document promotes conformance to other specifications as part of
accessible design. Conformance to specifications makes it easier to design
assistive technologies, and helps ensure that built-in accessibility functions
are implemented.

This document also includes some requirements to implement an accessibility
feature that may only be optional in another specification.

In rare cases, a requirement in UAAG 1.0 may conflict with a requirement in
another specification. UAAG 1.0 does not include requirements for resolving
this conflict, but the authors of this document anticipate that developers will
consider accessibility implications in determining how to resolve the
conflict.

Installation is an important aspect of both accessibility and general
software usability. On platforms where a user can install a user agent, the
installation (and update) procedures need to be accessible. Furthermore, the
installation procedure should provide and install all components necessary to
satisfy the requirements of this document, as the risk of installation failure
increases with the number of components (e.g., plug-ins)
to be installed.

This document does not include a checkpoint requiring that installation
procedures be accessible. Since this document considers installation to be part
of software usage, the different aspects of installation (user interface,
documentation, operating
environment conventions, etc.) are already covered by the complete set of
checkpoints.

Some of the requirements of this document have security implications:
communication through APIs, allowing programmatic read and write access to
content and user interface control, etc.
This document assumes that features required by this document will be built on
top of an underlying security architecture. Consequently, unless permitted
explicitly in a checkpoint (as in
checkpoint 6.5), this document grants no conformance exemptions based on
security issues.

Developers should design user agents that enable communication with trusted
assistive technologies. Sensitive information that the user agent can access
through the user agent's user interface should also be available to assistive
technologies through secure means. For instance, if the user types a password
in the user agent user interface, do not communicate substitute characters
(such as asterisks) through an API, but rather the real password, properly
encrypted.

Note also that appropriate user agent behavior with respect to security may
depend on the user's context. For instance, hiding typed passwords with
asterisks is much less important for someone alone in a room than for someone
in a crowded room. Similarly, while unencrypted passwords rendered as
synthesized speech should not be broadcast in a crowded room, they may pose no
security risk if the user is wearing an earphone.

For information related to security, refer to "XML-Signature Syntax and
Processing"
[XMLDSIG] and "XML Encryption Syntax and Processing" [XMLENC].

This document emphasizes the goal of ensuring that users, including users
with disabilities, have control over their environment for accessing the Web.
Key methods for achieving that goal include: optional self-pacing,
configurability, device-independence, interoperability, direct support for both
graphical and auditory output, and adherence to published conventions. Chapter 2 addresses these issues in detail.

This document also acknowledges the importance of author preferences and the
proper implementation of specifications. However, this document includes
requirements to override certain author preferences when the user would not
otherwise be able to access that content.

Many of the requirements in this document give the user additional control
over behavior that would otherwise occur automatically. For instance, there is
a requirement to allow configuration to not open a viewport automatically (checkpoint 5.3) and one that
requires user confirmation before submitting a form (checkpoint 5.5). This type of
manual configuration option may be essential for some users with disabilities,
since automatic behavior may be disorienting or interfere with navigation.

This document includes requirements for users with a variety of
disabilities, in part because some users may have more than one disability. In
some cases, it may appear that two requirements contradict each other. For
instance, a user with a physical disability may prefer that the user agent
offer more automatic behavior (to reduce demand for physical effort) than a
user with a cognitive disability (for whom automatic behavior may cause
confusion). Thus, many of the requirements in this document involve
configuration as one way to ensure that a functionality designed to improve
accessibility for one user does not interfere with accessibility for another.
Also, since a default user agent setting may be useful for one user but
interfere with accessibility for another, this document prefers configuration
requirements to requirements for default settings. Finally, there may be some
cases where, for some content, a feature required by this document is
ineffective or causes content to be less accessible, making it imperative that
the user be able to turn off the feature.

To avoid the risk that users are overwhelmed by an abundance of
configuration options, this document includes requirements that promote ease of
configuration and documentation of accessibility features (see guideline 12).

Many requirements in this document promote different kinds of
independence:

Input and output device independence. This document includes some
requirements to promote device-independence natively, as well as requirements
for interoperability with assistive technologies that provide complementary
input and output functionalities.

Spatial independence. Some users may not navigate effectively in two-dimensional visual space (e.g., users who do
not use a pointing device) or may be constrained to one temporal dimension
(e.g., users of audio-only output).

Temporal independence. Some users (e.g., users with a physical or cognitive
disability) may not be able to interact with content that changes over time, or
interaction with content that is time-sensitive.

In meeting the goals of users with disabilities, user agent developers will
also to improve access to the Web for users in general. For example, users
without disabilities:

may have a text-only screen, a small screen, or a slow Internet connection
(e.g., via a mobile phone browser). These users are likely to benefit from the
same features that provide access to people with low vision or blindness.

may be in a situation where their eyes, ears, or hands are busy or
interfered with (e.g., driving to work, working in a noisy environment, etc.).
These users are likely to benefit from the same features that provide access to
people who cannot use a mouse or keyboard due to a visual, hearing, or physical
disability.

may not understand fluently the natural language of spoken content. These
users are likely to benefit from the same visual rendering of text equivalents that make spoken
language accessible to people with a hearing disability.

Software that satisfies the requirements of this document is expected to be
more flexible, manageable, extensible, and beneficial to all users. For
example, a user agent architecture that allows programmatic access to content and the
user interface will encourage software modularity and reuse, and will
enable operation by scripting tools and automated test engines in addition to
assistive technologies.

The twelve guidelines in this document state general principles for the
development of accessible user agents. Each guideline includes:

The guideline number.

The guideline title.

The rationale behind the guideline and identification of some groups of
users who benefit from it.

A list of checkpoint definitions. This list may be split into groups of
related checkpoints. For instance, the list might be split into one group of
"checkpoints for visually rendered text" and second group of "checkpoints for
audio volume control"." Within each group, checkpoints are ordered according to
their priority, e.g., Priority 1 before Priority 2.
Within a guideline, checkpoint groupings and checkpoint order have no bearing
on conformance.

Each checkpoint definition includes the following parts. Some parts are normative (i.e., relate to conformance);
others are informative only.

The checkpoint number.

The checkpoint title. This title is not a requirement, but rather is a
phrase to help readers remember an important requirement made by the checkpoint
provision(s). (Informative)

A link to the Techniques document [UAAG10-TECHS] for more
information about the checkpoint: rationale, who benefits, example techniques,
references, and more. (Informative)

A list of one or more checkpoint provisions, which embody
the requirements of the checkpoint. These requirements must be satisfied by the
user agent for conformance. (Normative)

Techniques that are sufficient for satisfying all or part of a checkpoint.
(Normative when present)

Normative
inclusions and exclusions. These are qualifications about what is required
(inclusion) or is not required (exclusion) to satisfy the checkpoint. Some of
the inclusions are reminders about what may be required for conformance:

When a checkpoint may be excluded from a conformance profile, it is
identified by a conformance profile label. See
the section on conformance profiles for
more information on how a user agent may conform to this document even though
it does not satisfy every checkpoint.

(Normative when present)

Notes about the checkpoint (beginning with the word
"Note"). The notes clarify the scope of the checkpoint through
further description, examples, cross references, and commentary. (Informative
when present)

First-time readers of the document are encouraged to read the full context
provided for each checkpoint, including the guideline prose, the surrounding
checkpoints (since nearby checkpoints are generally related), notes after
checkpoints, and associated techniques (in the Techniques document
[UAAG10-TECHS]). The checklist [UAAG10-CHECKLIST] is
also a useful tool (e.g., for evaluating a user agent for conformance), but
does not provide the same contextual support.

The checkpoints in this document are not generally technology-specific. They
have been designed to be largely technology-independent in order to make sense
for a variety of existing and future technologies. The Techniques document
[UAAG10-TECHS] is an important resource to help developers understand how to
apply the requirements to HTML, CSS, SMIL, and SVG, and several operating
environments.

Each checkpoint is a "minimal" requirement that must be satisfied for conformance. Developers can always implement features
beyond those required by this document. In some cases, it may be easier (or
just better design) to implement a general feature rather than one that meets
only the narrow requirement of a single checkpoint. For example, a navigable
structure view of content that allows users to query elements for their
properties is likely to benefit all users and may be used to satisfy a number
of requirements of this document.

Some requirements have a wider impact than others. For instance, the
keyboard requirements of
checkpoint 1.1 have an impact on all other requirements in the document
related to user input: any requirement that involves user input must be
satisfied through the keyboard. Because the keyboard requirements of checkpoint 1.1 have been
factored out, the other checkpoints are shorter; they are written "Allow
configuration" instead of "Allow configuration so that, through the keyboard,
..."

If the user agent does not satisfy this checkpoint, one or more groups of
users with disabilities will find it impossible to access the Web. Satisfying
this checkpoint is a basic requirement for enabling some people to access the
Web.

If the user agent does not satisfy this checkpoint, one or more groups of
users with disabilities will find it difficult to access the Web. Satisfying
this checkpoint will remove significant barriers to Web access for some
people.

Ensure that the user can interact with
the user agent (and the content it renders) through
different input and output devices.

Since people use a variety of devices for input and output, user agent
developers need to ensure redundancy in the
user interface. The user may have to operate the user interface with a
variety of input devices (keyboard, pointing device, voice input, etc.) and
output modalities (e.g., graphical, speech, or
braille rendering).

Though it may seem contradictory, enabling full user agent operation through
the keyboard is an important part of promoting device-independence given
today's user agents. In addition to the fact that some form of keyboard is
supported in most operating environments, there are several reasons for
this:

For some users (e.g., users with blindness or physical disabilities),
operating a user agent with a pointing device may be difficult or impossible
since it requires tracking the pointing device position in a two-dimensional visual space. Keyboard operation
generally makes fewer perceptual/motor demands for moving the pointing device
to a visual target.

Some assistive technologies that support a diversity of input and output
mechanisms use keyboard APIs for
communication with some user agents; see checkpoint 6.7. People who cannot or do not use a pointing
device may interact with the user interface with the keyboard, through voice
input, a head wand, touch screen, or other device.

While this document only requires keyboard operation for conformance, it promotes input device independence by
also allowing people to claim conformance for full pointing device support or
full voice support.

As a way to promote output device independence, this guideline requires
support for text messages in the user interface because text may be rendered
either visually, as synthesized speech, or as braille.

Spatial (e.g., when the keyboard is used to move the pointing device in two-dimensional visual space to manipulate a
bitmap image).

User agents should support direct or sequential keyboard operation for all
functionalities. Furthermore, the user agent should satisfy this checkpoint by
offering a combination of keyboard-operable user interface controls (e.g.,
keyboard operable print menus and settings) and direct keyboard shortcuts
(e.g., to print the current page).

It is also possible to claim conformance to this
document for full support through pointing device input and/or voice input. See
the section on Input modality labels.

Provision one of this checkpoint applies to handlers of any input
device event type, including event types for keyboard, pointing device, and
voice input.

The user agent is not required to allow activation of event handlers
associated with a given device (e.g., the pointing device) in any order other
than what the device itself allows (e.g., a mouse down event followed by a
mouse drag event followed by a mouse up event).

The requirements for this checkpoint refer to any
explicitly associated input device
event handlers associated with an element, independent of the input modalities for which the user agent
conforms. For example, suppose that an element has an explicitly associated
handler for pointing device events. Even when the user agent only conforms for
keyboard input (and does not conform for the pointing device, for example),
this checkpoint requires the user agent to allow the user to activate that
handler with the keyboard.

Note: For example, if the user is alerted of an event by an
audio cue, a visually-rendered text equivalent in the status bar could satisfy
this checkpoint. Per checkpoint
6.5, a text equivalent for each such message must be available through an
API. See also
checkpoint 6.6 for
requirements for programmatic notification of changes to the user
interface.

Ensure that users have access to all content,
notably conditional content that may have
been provided to meet the requirements of the Web Content Accessibility
Guidelines 1.0
[WCAG10].

The checkpoints in this section require the user agent to provide access to
all content through a series of complementary mechanisms designed so that if
one fails, another will provide some access. The following preferences are
embodied in the checkpoints:

Both manual and automatic selection of which conditional content to render are
important to accessibility.

Both structured navigation and unstructured access to content are important
to accessibility.

Rendering according to format specification is preferred, but a source view
of text content may be necessary for access (e.g., because of user-side error
conditions, authoring errors, inadequate specification, or incorrect user agent
implementation). For example, in order to find necessary information, the user
may have to look at Uniform Resource Identifiers (URIs) for
information, HTML comments, XML element
names, or script data.

Configuration and control of rendering are important for access. For
instance, the user agent should respect authoring synchronization cues for
content that changes over time, but also needs to allow the user to control the
time intervals when user input might otherwise be possible.

Authors may use the conditional
content mechanisms of a specification to satisfy the requirements of the
Web Content Accessibility Guidelines 1.0 [WCAG10]. Ensuring access to conditional content benefits all
users since some users may not have access to some content due to a
technological limitation (e.g., their mobile browser cannot display graphics)
or simply a configuration preference (e.g., they have a slow Internet
connection and prefer not to download movies or images).

Rendering requirements include format-defined interactions between author
preferences and user preferences/capabilities (e.g., when to render the
"alt" attribute in HTML, the rendering order of
nested OBJECT elements in HTML, test attributes in SMIL, and the
cascade in CSS2).

When a rendering requirement of another specification contradicts a
requirement of UAAG 1.0, the user agent may disregard the rendering requirement
of the other specification and still satisfy this checkpoint; see the section
on the relation of this document to general software
design guidelines and other specifications. for more information.

The user agent is not required to satisfy this checkpoint for all
implemented specifications; see the section on
conformance profiles for more information.

For content
authored in text formats, provide a view of the text source. For the purposes of this
checkpoint, a text format is any media object given an Internet media type of
"text" (e.g., "text/plain", "text/html", or "text/*") as defined in RFC 2046
[RFC2046], section 4.1.

The user agent is only required to satisfy this checkpoint for text formats
that are part of a conformance claim; see the section on conformance profiles for more information.
However, user agents should provide a text view for all implemented text
formats.

To satisfy provision one of this checkpoint, the configuration may be a
switch that, for all content, turns on or off the access mechanisms described
in provision two.

To satisfy provision two of this checkpoint, the user agent may provide
access on a per-element basis (e.g., by allowing the user to query individual
elements) or for all elements (e.g., by offering a configuration to render
conditional content all the time).

Note: For instance, an HTML user agent might allow users to
query each element for access to conditional content supplied for the
"alt", "title", and "longdesc"
attributes. Or, the user agent might allow configuration so that the value of
the "alt" attribute is rendered in place of all IMG
elements (while other conditional content might be made available through
another mechanism).

The user agent may satisfy this checkpoint by pausing processing
automatically to allow for user input, and resuming processing on explicit user request. When
this technique is used, pause at the end of each time interval where user input
is possible. In the paused state:

Alert the user that the rendered content has been paused
(e.g., highlight the pause button in a multimedia player's control panel).

Allow the user to resume on explicit user request (e.g., by
pressing the play button in a multimedia player's control panel; see also checkpoint 4.5).

The user agent may satisfy this checkpoint by generating a
time-independent (or, "static") view, based on the original content, that offers the user the same
opportunities for interaction. The static view should reflect the structure and
flow of the original time-sensitive presentation; orientation cues will help
users understand the context for various interaction opportunities.

When satisfying this checkpoint for a real-time presentation, the user
agent may discard packets that continue to arrive after the construction of the
time-independent view (e.g., when paused or after the construction of a static
view).

This checkpoint does not apply when the user
agent cannot recognize the time interval in the
presentation format, or when the user agent cannot control the timing (e.g.,
because it is controlled by the server).

Note: If the user agent satisfies this checkpoint by
pausing automatically, it may be necessary to pause more than once when there
are multiple opportunities for time-sensitive user interaction. When pausing,
pause synchronized content as well (whether rendered in the same or different
viewports) per checkpoint
2.6. In SMIL 1.0
[SMIL], for example, the "begin", "end",
and "dur" attributes synchronize
presentation components. See also checkpoint 3.5, which involves client-driven content
retrieval.

The user agent may satisfy this checkpoint by basing the repair text on any
of the following available sources of information: URI reference, content type,
or element type. Note, however, that additional information that would enable
more helpful repair might be available but not "near" the missing conditional
content. For instance, instead of generating repair text on a simple URI
reference, the user agent might look for helpful information near a different
instance of the URI reference in the same document object, or might retrieve
useful information (e.g., a title) from the resource designated by the URI
reference.

Note: In some authoring scenarios,
empty content (e.g., alt="" in HTML) may make an appropriate
text equivalent, such as when non-text content has no other
function than pure decoration, or when an image is part of a "mosaic" of
several images and does not make sense out of the mosaic. Refer to the Web
Content Accessibility Guidelines 1.0 [WCAG10] for more information about
text equivalents.

Note: For instance, an HTML user agent might allow
configuration so that the value of the "alt" attribute is rendered in place of all
IMG elements (while other conditional content might be made
available through another mechanism). The user agent may offer multiple
configurations (e.g., a first configuration to render one type of conditional
content automatically, a second to render another type, etc.).

This checkpoint does not require the user agent to allow different
configurations for different natural languages.

Note: This checkpoint is designed primarily to benefit
users with serial access to content or who navigate sequentially, allowing
them to skip portions of content that would be unusable if rendered as
"garbage".

Ensure that the user may turn off rendering of
content (audio, video, scripts, etc.) that may reduce accessibility by
obscuring other content or disorienting the user.

Some content or behavior specified by the author may make the user agent
unusable or may obscure information. For instance, flashing content may trigger
seizures in people with photosensitive epilepsy, or may make a Web page too
distracting to be usable by someone with a cognitive disability. Blinking text
can affect screen reader users, since screen readers (in conjunction with
speech synthesizers or braille displays) may re-render the text every time it
blinks. Distracting background images, colors, or sounds may make it impossible
for users to see or hear other content. Dynamically changing Web content may
cause problems for some assistive technologies. Scripts
that cause unanticipated changes (viewports that open,
automatic content retrieval, etc.) may disorient some users with cognitive
disabilities.

This guideline requires the user agent to allow configuration so that, when
loading Web resources, the user agent does not
render content in a manner that might pose accessibility problems. Requirements
for interactive control of rendered content are part of guideline 4.

The user agent may satisfy this checkpoint with a configuration to not
render any images, including background images. However, user agents
should satisfy this checkpoint by allowing users to turn off background images
alone, independent of other types of images in
content.

When configured not to render background images, the user agent is not
required to retrieve them until the user requests them explicitly. When
background images are not rendered, user agents should render a solid
background color instead; see checkpoint 4.3 for information about text colors.

This checkpoint only requires control of background images for "two-layered
renderings", i.e., one rendered background image with all other content
rendered "above it".

This configuration is required for content rendered without any user
interaction (including content rendered on load or as the result of a script),
as well as content rendered as the result of user interaction that is not an explicit user request (e.g.,
when the user activates a link).

Note: See
guideline 4 for additional requirements related to the control of rendered
audio, video, and animated images. When these content types are not rendered,
they are considered conditional
content. See checkpoint
2.3 for information about providing access to conditional content.

Note: Animation (a rendering effect) differs from streaming
(a delivery mechanism). Streaming content might be rendered as an animation
(e.g., an animated stock ticker or vertically scrolling text) or as static text
(e.g., movie subtitles, which are rendered for a limited time, but do not give
the impression of movement).

Note: Scripts and applets may provide very useful
functionality, not all of which causes accessibility problems. Developers
should not consider that the user's ability to turn off scripts is an effective
way to improve content accessibility; turning off scripts means losing the
benefits they offer. Instead, developers should provide users with finer
control over user agent or content behavior known to raise accessibility
barriers. The user should only have to turn off scripts as a last resort.

When the user chooses not to retrieve (fresh) content, the user agent may
ignore that content; buffering is not required.

The user agent is not required to satisfy this checkpoint for "client-side
redirects", i.e., author-specified instructions that a piece of content is
temporary and intermediate, and is replaced by content that results from a
second request. Authors (and Webmasters) should use the redirect mechanisms of
HTTP instead of client-side redirects.

This checkpoint only applies when the user agent (not the server)
automatically initiates the request for fresh content.

Note: For example, if an HTML author has used a
META element for automatic content retrieval, allow configuration to
override the automatic behavior with manual confirmation.

Providing access to content (see guideline 2) includes enabling users to configure and control
its rendering. Users with low vision may require that text be rendered at a
size larger than the size specified by the author or by the user agent's
default rendering. Users with color blindness may need to impose or prevent
certain color combinations.

For dynamic presentations such as synchronized multimedia presentations
created with SMIL 1.0
[SMIL], users with cognitive, hearing, visual, and physical
disabilities may not be able to interact with a presentation within the time
frame assumed by the author. To make the presentation accessible to these
users, user agents rendering multimedia content (audio, video, and other animations), have to allow the user to
control the playback rate of this content, and also to stop, start, pause, and
navigate it quickly. User agents rendering audio have to allow the user to
control the audio volume globally and to allow the user to control
distinguishable audio tracks.

User agents with speech synthesis capabilities need to allow users to
control various synthesized speech rendering parameters. For instance, some
users may not be able to make use of high or low frequencies; these users have
to be able to configure their speech synthesizers to use suitable
frequencies.

The user agent may satisfy provision one of this checkpoint through a
number of mechanisms, including zoom, magnification, and allowing the user to
configure a reference size for rendered text (e.g., render text at 36 points
unless otherwise specified). For example, for CSS2 [CSS2] user agents, the 'medium'
value of the 'font-size' property corresponds to a reference size.

The word "scale" is used in this checkpoint to mean the general size of
text.

The user agent is not required to satisfy this requirement through
proportional scaling. What must hold is that if rendered text A is smaller than
rendered text B at one value of this configuration setting, then text A will
still be smaller than text B at another value of this configuration
setting.

Note: User configuration of foreground and background
colors may inadvertently lead to the inability to distinguish ordinary text
from selected text, focused text, etc. See checkpoint 10.2 for more
information about highlight styles.

Allow the user to slow the presentation rate
of rendered audio and animation content (including
video and animated images).

As part of satisfying provision one of this
checkpoint, for a visual track, provide at
least one setting between 40% and 60% of the original speed.

As part of satisfying provision one of this
checkpoint, for a prerecorded audio track including audio-only presentations,
provide at least one setting between 75% and 80% of the original speed.

When the user agent allows the user to slow
the visual track of a synchronized multimedia presentation to between 100% and
80% of its original speed, synchronize the visual and audio tracks (per checkpoint 2.6). Below 80%,
the user agent is not required to render the audio
track.

The user agent is not required to satisfy this checkpoint for audio and
animations whose recognized role is to create a purely
stylistic effect. Purely stylistic effects include background sounds,
decorative animated images, and effects caused by style sheets.

Note: The style exception of this checkpoint is based on
the assumption that authors have satisfied the requirements of the "Web Content
Accessibility Guidelines 1.0" [WCAG10] not to convey information
through style alone (e.g., through color alone or style sheets alone).

The user agent may satisfy the navigation requirement of provision two of
this checkpoint through forward and backward
serial access techniques (e.g., advance five seconds), or direct access
techniques (e.g., play starting at the 10-minute mark), or some
combination.

When serial access techniques are used to
satisfy provision two of this checkpoint, the user agent is not required to
play back content during advance or rewind (though doing so may help orient the
user).

When the user pauses a real-time audio or animation, the user agent may
discard packets that continue to arrive during the pause.

This checkpoint applies to content that is either rendered automatically
(e.g., on load) or on explicit request from the user.

The user agent is not required to satisfy this checkpoint for audio and
animations whose recognized role is to create a purely
stylistic effect; see checkpoint
4.4 for more information about what constitutes a stylistic effect.

The user control required by this checkpoint includes the ability to override author-specified volumes for the
relevant sources of audio.

The user agent is not required to satisfy this checkpoint for audio whose
recognized role is to create a purely
stylistic effect; see checkpoint
4.4 for more information about what constitutes a stylistic effect.

Note: The user agent should satisfy this checkpoint by
allowing the user to control independently the volumes of all audio sources (e.g., by implementing a general
audio mixer type of functionality). See checkpoint 4.10 for information about controlling the volume
of synthesized speech.

Note: This checkpoint is more specific than checkpoint
4.11. It requires support for the voice characteristics listed in the
provisions of this checkpoint. Definitions for these characteristics are based
on descriptions in section 19 of the Cascading Style Sheets Level 2
Recommendation
[CSS2]; refer to that specification for additional informative descriptions. Some speech
synthesizers allow users to choose values for synthesized speech
characteristics at a higher abstraction layer, i.e., by choosing from present
options distinguished by "gender", "age", "accent", etc. Ranges of values may
vary among speech synthesizers.

Note: Definitions for the functionalities listed in the
provisions of this checkpoint are based on descriptions in section 19 of the
Cascading Style Sheets Level 2 Recommendation [CSS2]; refer to that specification
for additional informative descriptions.

This checkpoint only applies to user agents that support
style sheets.

Note: By definition, the user agent's default style
sheet is always present, but may be overridden by author or user styles.
Developers should not consider that the user's ability to turn off author and
user style sheets is an effective way to improve content accessibility; turning
off style sheet support means losing the many benefits they offer. Instead,
developers should provide users with finer control over user agent or content
behavior known to raise accessibility barriers. The user should only have to
turn off author and user style sheets as a last resort.

Ensure that the user can control the behavior
of viewports and user interface controls, including those that may be
manipulated by the author (e.g., through scripts).

Control of viewport behavior is important to
accessibility. Unexpected changes to the point of regard – what the user
is presumed to be viewing – may cause users to lose track of how many viewports are open, which viewport has the
current focus, etc. If carried out
automatically, these changes might go unnoticed (e.g., by some users with
blindness) or be disorienting (e.g., to some users with a cognitive
disability). This guideline includes requirements for control of opening and
closing viewports, the relative position of graphical viewports, changes to
focus, and inadvertent form submissions.

When configured per provision one of this
checkpoint, instead of opening a viewport automatically, alert the user and
allow the user to open it with an explicit request (e.g., by
confirming a prompt or following a link generated by the user agent).

If a viewport (e.g., a frame set) contains other viewports, these
requirements only apply to the outermost container viewport.

User creation of a new viewport (e.g., empty or with a new resource loaded)
through the user agent's user interface constitutes an explicit user
request.

Note: Generally, viewports open automatically as the result
of instructions in content. See also checkpoint 5.1 (for
control over changes of focus when a viewport opens) and checkpoint 6.6 (for
programmatic notification of changes to the user interface).

Note: For example, if users navigating links move to a
portion of the document outside a graphical viewport, the viewport should
scroll to include the new location of the focus. Or, for users of audio
viewports, allow configuration to render the selection or focus immediately
after the change.

Configuration is preferred, but it not required if forms can only ever be
submitted on explicit user request.

Note: Examples of automatic form submission include:
script-driven submission when the user changes the state of a particular form
control associated with the form (e.g., via the pointing device), submission
when all fields of a form have been filled out, and submission when a
"mouseover" or "change" event
occurs.

This guideline addresses interoperability between a conforming user agent
and other software, in particular assistive technologies. The
checkpoints of this guideline require implementation of application programming
interfaces (APIs) for
communication. There are three types of requirements in this guideline:

Requirements for what information must be communicated through an
API.

Requirements for which APIs or types of
APIs must be used to communicate this information.

Requirements for additional characteristics of these
APIs.

Note: The User Agent Accessibility Guidelines Working Group
believes that, in order to promote interoperability between a conforming user
agent and more than one assistive technology, it is more important to
implement conventional APIs than custom
APIs, even though custom APIs may offer
specialized access.

Provide access to the content required in checkpoint 6.1 by conforming to the following modules of the
W3C Document Object Model DOM
Level 2 Core Specification [DOM2CORE] and exporting bindings
for the interfaces they define:

The user agent is not required to export the bindings outside of the user
agent process (though doing so may be useful to assistive technology
developers).

Note: Refer to the "Document Object Model (DOM) Level 2
Core Specification" [DOM2CORE] for information about
HTML and XML versions covered. This
checkpoint is stands apart from
checkpoint 6.1 to emphasize the distinction between what information is
required and how to provide access to that information.

"Structured programmatic access" means access through an API to recognized
information items of the content (such as the information items of the XML
Infoset
[INFOSET]). Plain text has little structure, so an API that provides
access to it will be correspondingly less complex than an API for XML content.
For content more structured than plain text, an API that only provides access
to a stream of characters does not satisfy the requirement of providing
structured programmatic access. This document does not otherwise define what is
sufficiently structured access.

An API is considered "available" if the specification of the API is
published (e.g., as a W3C Recommendation) in time for integration into a user
agent's development cycle.

For graphical user agents, make
available bounding dimensions and coordinates of rendered graphical objects.
Coordinates must be relative to the point of origin in the graphical
environment (e.g., with respect to the desktop), not the viewport.

For graphical user agents, provide
access to the following information about each piece of rendered text: font
family, font size, and foreground and background colors.

As part of satisfying provisions one
and two of this checkpoint, implement at least one API according to the API
cascade described in provision two of checkpoint 6.3.

Note: User agents should provide programmatic access to
additional useful information about rendered content that is not available
through the APIs required by checkpoints 6.2 and
6.3, including the correspondence (in both directions) between graphical
objects and their source in the document object, and information
about the role of each graphical object.

Note: APIs used to satisfy the requirements of this
checkpoint may be independent of a particular operating environment (e.g., the
W3C DOM), conventional APIs for a particular operating environment,
conventional APIs for programming languages, plug-ins,
virtual machine environments, etc. User agent developers are encouraged to
implement APIs that allow assistive technologies to interoperate with multiple
types of software in a given operating environment (user agents, word
processors, spreadsheet programs, etc.), as this reuse will benefit users and
assistive technology developers. User agents should always follow operating
environment conventions for the use of input and output APIs.

The user agent is not required to provide notification of changes in the
rendering of content (e.g., due to an animation effect or an effect
caused by a style sheet) unless the document object to make those
changes.

Note: Support for character encodings is important so that
text is not "broken" when communicated to assistive technologies. For example,
the DOM Level 2 Core Specification [DOM2CORE], section 1.1.5
requires that the DOMString type be encoded using UTF-16.

Note: For example, the programmatic exchange of information
required by other checkpoints in this document should be efficient enough to
prevent information loss, a risk when changes to content or user interface
occur more quickly than the communication of those changes. Timely exchange is
also important for the proper synchronization of alternative renderings. The
techniques for this checkpoint explain how developers can reduce communication
delays. This will help ensure that assistive technologies have timely access to
the document object model and other
information that is important for providing access.

Following operating
environment conventions also increases predictability for users and for
developers of assistive
technologies. These guidelines explain what users will expect from the look
and feel of the user interface, keyboard conventions, documentation, etc. These
guidelines also include information about accessibility features that the user
agent should adopt rather than reimplement.

Note: Information about operating environment accessibility
conventions is available in the Techniques document
[UAAG10-TECHS]. See checkpoint 11.5 for information about the user agent's
default input configuration.

Note: For example, in some operating environments, when a
functionality may be triggered through a menu and through the keyboard, the
developer may design the menu entry so that the character of the activating key
is also shown. See
checkpoint 11.5 for information about the user agent's default input
configuration.

Support the accessibility features
of all implemented specifications. Implement W3C Recommendations when available
and appropriate for a task.

Developers should implement open specifications. Conformance to open
specifications benefits interoperability and accessibility by making it easier
to design assistive
technologies (also discussed in guideline 6).

While developers should implement the accessibility features of any
specification (checkpoint 8.1), this document recommends conformance to W3C
Recommendations in particular (checkpoint 8.2) for several reasons:

W3C specifications include "built-in" accessibility features.

W3C specifications undergo early review to ensure that accessibility issues
are considered during the design phase. This review includes review from
stakeholders in accessibility.

W3C specifications are developed in a consensus process (refer to the
process defined by the W3C Process Document [W3CPROCESS]). W3C encourages
the public to review and comment on these specifications (public Working
Drafts, Candidate Recommendations, and Proposed Recommendations). For
information about how specifications become W3C Recommendations, refer to the
W3C Recommendation track ([W3CPROCESS], section 6.2). W3C
Recommendations (and other technical
reports) are published at the W3C Web site.

When a requirement of another specification contradicts a requirement of
the current document, the user agent may disregard the requirement of the other
specification and still satisfy this checkpoint.

Users should be able to navigate to important pieces of content within a
configurable view, identify the type of object they have navigated to, interact
with that object easily (if it is an enabled element), and review the
surrounding context (to orient themselves). Providing a variety of navigation
and search mechanisms helps users with disabilities (and all users) access
content more efficiently. Navigation and searching are particularly important
to users with serial access to content or who navigate sequentially.

Direct navigation (e.g., to a particular link or paragraph) is faster than
sequential navigation, but
generally requires familiarity with the content. Direct navigation is important
to users with some physical disabilities (who may have little or no manual
dexterity and/or increased tendency to push unwanted buttons or keys), to users
with visual disabilities, and also benefits "power users." Direct navigation
may be possible with the pointing device or the keyboard (e.g., keyboard
shortcuts).

Structured navigation mechanisms offer both context and speed. User agents
should allow users to navigate to content known to be structurally important:
blocks of content, headers and sections, tables, forms and form elements,
enabled elements, navigation mechanisms, containers, etc. For information about
programmatic access to document structure, see guideline 6.

User agents should allow users to configure navigation mechanisms (e.g., to
allow navigation of links only, or links and headings, or tables and forms,
etc.).

When a viewport includes no enabled elements (either because the format
does not provide for this, or a given piece of content has no enabled
elements), the content focus requirements of the following checkpoints do not
apply: 1.2, 5.1, 5.4, 6.6, 7.1, 9.3, 9.4, 9.5, 9.6, 9.7, 10.2, and 11.5.

Note: For example, when two frames of a frameset contain
enabled elements, allow the user to make the
content focus of either frame the current focus. Note that viewports
"owned" by plug-ins that are part of a conformance claim
are also covered by this checkpoint. See checkpoint 7.1 for
information about implementing content focus according to operating environment
conventions.

Note: In addition to forward sequential navigation, the
user agent should also allow reverse sequential navigation. See checkpoint 9.9 for information
about structured navigation. See checkpoints 5.1 and 6.6 for more information
about focus changes.

The viewport history associates values for these three state variables (point of regard, content focus, and selection) with a particular document
object. If the user returns to a state in the history and the user agent
retrieves new content, the user agent is not required to restore the saved
values of the three state variables.

Note: For instance, in this configuration for an HTML
document, do not activate any handlers for the 'onfocus',
'onblur', or 'onchange' attributes. In this
configuration, user agents should still apply any stylistic changes (e.g., highlighting) that may occur when there is
a change in content focus.

Note: For example, allow the user to query the element with
content focus for the list of input device event types, or add them directly to
the sequential navigation order
described in checkpoint 9.3. See
checkpoint 1.2
for information about activation of event handlers associated with the element
with focus.

Allow the user to navigate efficiently to and among important structural
elements in rendered content.

As part of satisfying provision one of this checkpoint, allow forward and
backward sequential
navigation.

Note: This specification intentionally does not identify
which "important elements" must be navigable as this will vary by
specification. What constitutes "efficient navigation" may depend on a number
of factors as well, including the "shape" of content (e.g., sequential
navigation of long lists is not efficient) and desired granularity (e.g., among
tables, then among the cells of a given table). Refer to the Techniques
document [UAAG10-TECHS] for
information about identifying and navigating important elements.

Provide information that will help the user
understand browsing context.

All users require clues to help them understand their "location" when
browsing: where they are, how they got there, where they can go, what's nearby,
etc. Some mechanisms that provide such clues through the user interface
(visually, as audio, or as braille) include:

information about the current state of the user's interaction with content:
where the viewport is in content (shown, for example, through proportional
scroll bars), which viewport has the
current focus, where the user has selected content, a history mechanism,
the title of the current document or frame, etc.

information about specific elements, such as the dimensions of a table, the
length of an audio clip, the structure of a form, etc.

information about relationships among elements, such as between table cells
and related table headers.

information about the structure of content, e.g., through an outline view
of a document.

Orientation mechanisms such as these are especially important to users with
serial access to content or who navigate sequentially. For
instance, these users cannot "scan" a graphically displayed table with their
eyes for information about a table cell's headers, neighboring cells, etc. User
agents need to provide other means for users to understand table cell
relationships, frame relationships (what relationship does the graphical layout
convey?), form context (have I filled out the form completely?), link
information (have I already visited this link?), etc.

For graphical user interfaces, as part
of satisfying provision one of this checkpoint, if a highlight mechanism
involves text size, font family,
rendered text foreground and background colors, or text decorations, offer
at least the following range of values:

for text size, the range required by provision three of checkpoint 4.1.

for font family, the range required by provision three of checkpoint 4.2.

for text foreground and background colors and decorations, the range
offered by the conventional utility available in the operating environment for
users to choose rendered text colors or decorations (e.g., the standard font
and color dialog box resources supported by the operating system). If no such
utility is available, the range supported by the conventional APIs of the
operating environment for specifying text colors or drawing text.

Highlight enabled elements according to the
granularity specified in the format. For example, an HTML user agent rendering
a PNG image as part of a client-side image map is only required to highlight
the image as a whole, not each enabled region. An SVG user agent rendering an
SVG image with embedded graphical links is required to highlight each (enabled) link that may be rendered
independently according to the SVG specification.

Note: Examples of highlight mechanisms for selection and
content focus include foreground and background color variations, underlining,
distinctive synthesized speech prosody, border styling, etc. Because the
selection and focus change frequently, user agents should not highlight them
using mechanisms (e.g., font size variations) that cause content to reflow, as
this may disorient the user. Graphical highlight mechanisms that generally do
not rely on rendered text foreground and background color alone include
underlines or border styling. Per checkpoint 7.1, follow operating environment conventions
that benefit accessibility when implementing the selection and content focus.
For instance, if specified at the level of the operating environment, inherit
the user's preferences for selection styles.

Make available to the user an "outline"
view of rendered content, composed of labels
for important structural elements (e.g., heading text, table titles, form
titles, and other labels that are part of the content).

What constitutes a label is defined by each markup language specification.
For example, in HTML, a heading (H1-H6) is a label
for the section that follows it, a CAPTION is a label for a table,
the "title" attribute is a label for its element, etc.

The user agent is not required to generate a label for an important element
when no label is present in content. The user agent may generate a label when
one is not present.

Note: This outline view will provide the user with a
simplified view of content (e.g, a table of contents). For information about
what constitutes the set of important structural elements, see the Note
following checkpoint 9.9. By
making the outline view navigable, it is possible to satisfy this checkpoint
and checkpoint 9.9 together:
allow users to navigate among the important elements of the outline view, and
to navigate from a position in the outline view to the corresponding position
in a full view of content. See checkpoint 9.10 for additional configuration options.

For graphical viewports, as part of
satisfying provision one of this checkpoint, provide at least one highlight
mechanism that does not rely on
rendered text foreground and background colors alone (e.g., use a thick
outline).

The user agent may calculate the relative position according to content
focus position, selection position, or viewport position, depending on how the
user has been browsing.

The user agent may indicate the proportion of content viewed in a number of
ways, including as a percentage, as a relative size in bytes, etc. See checkpoint 1.3 for more information
about text versions of messages to the user, including messages about position
information.

Allow users to configure the user agent so that
frequently performed tasks are made convenient, and allow users to save their
preferences.

Web users have a wide range of capabilities and need to be able to configure the user agent according to their
preferences for styles, graphical user interface configuration, keyboard
configuration, etc. Most of the checkpoints in this guideline pertain to the
input configuration: how user agent behavior is controlled through keyboard
input, pointing device input, and voice input. An input configuration is the
set of "bindings" between user agent functionalities and user interface input mechanisms.

To satisfy this checkpoint, the user agent may make available binding
information in a centralized fashion (e.g., a list of bindings) or a
distributed fashion (e.g., by listing keyboard shortcuts in user interface
menus). See related documentation checkpoints 12.2, 12.3, and 12.5.

Note: For example, for HTML documents, provide a view of
keyboard bindings specified by the author through the "accesskey"
attribute. The intent of this checkpoint is to centralize information about
author-specified bindings so that the user does not have to read an entire
document to look for available bindings.

Allow the user to override any binding in the user agent
default keyboard configuration with a binding to either a key plus modifier
keys or to a single key.

For
each functionality in the set required by checkpoint 11.5, allow the user to
configure a single-key binding. A single-key binding is one where a single
key press performs the task, with zero modifier keys.

Provision two of this checkpoint does not require single physical key
bindings for character input, only for the activation of user agent
functionalities.

If the number of physical keys on the keyboard is less than the number of
functionalities required by checkpoint 11.5, then provision two of this checkpoint does
not require the user agent to allow single-key bindings for all of the
functionalities. The user agent should give preference to those functionalities
listed in provision one of
checkpoint 11.5.

This checkpoint is mutually exclusive of checkpoint 11.3 since it is specific to the keyboard and to
emphasize the importance of easy keyboard access.

Note: Because single-key access is so important to some
users with physical disabilities, user agents should ensure that: (1) most keys
of the physical keyboard may be configured for single-key bindings, and (2)
most functionalities of the user agent may be configured for single-key
bindings. For information about access to user agent functionality through a
keyboard API, see checkpoint
6.7.

The user agent may satisfy the functionality of entering a URI for a new
resource in a number of ways, including by prompting the user or by moving the
user interface focus to a control for entering
URIs.

Note: This checkpoint does not make any requirements about
the ease of use of default input configurations, though clearly the default
configuration should include single-key bindings and allow easy operation. Ease
of use is addressed by the configuration requirements of checkpoint 11.3.

Ensure that the user can learn about software
features that benefit accessibility from the documentation. Ensure that the
documentation is accessible.

Documentation of the user interface is important, as is documentation of the
user agent's underlying functionalities. While intuitive user interface design
is valuable to many users, some users may still not be able to understand or be
able to operate the native user interface without thorough documentation. For
instance, a user with blindness may not find a graphical user interface
intuitive without supporting documentation.

For the purposes of this checkpoint, a user agent feature that benefits
accessibility is one implemented to satisfy the requirements of this document
(including the requirements of checkpoints 8.1 and 7.3, and the API requirements of
guideline 6).

Note: The help system should include discussion of user
agent features that benefit accessibility. The user agent should satisfy this
checkpoint by providing both centralized and integrated views of accessibility
features in the documentation.

If the user agent does not allow the user to override the default user
agent input configuration (see
checkpoint 11.3), the documentation used to satisfy this checkpoint also
satisfies checkpoint
11.1.

A user agent conforms to this document by satisfying the requirements
identified by a conformance profile. This
normative section explains:

How to construct a conformance profile.
A user agent is not required to satisfy every requirement in this document in
order to conform.

How to make a conformance claim, i.e., a
statement about how a chosen user agent satisfies the requirements identified
by a chosen conformance profile. See the section on target
user agents in the introduction for information about which user agents are
expected to conform.

Conformance to the requirements of this document is expected to be a strong
indicator of accessibility, but it may be neither a necessary nor a sufficient
condition for ensuring the accessibility of software. Thus, some software may
not conform to this document but still be accessible to some users with
disabilities. Conversely, some software may conform to this document but still
be inaccessible to some users with disabilities. Some requirements of this
document may not benefit some users for some content, but the requirements are
expected to benefit many users with disabilities, for general purpose content.
For more information, see the section on known
limitations of this document, and the section on restricted functionality and
conformance.

This document demands substantially more conformance flexibility than can be
achieved using the terms "must", "should", and "may" alone, as defined in RFC
2119 [RFC2119]. Where "must", "should",
"required", and "may" appear in this document, they are used consistently with
RFC 2119 for a chosen conformance profile. The imperative voice (e.g., "Allow
configuration ...") used in the checkpoint provisions implies "must", but a
user agent is only obligated to satisfy the requirements of a chosen
conformance profile.

a list of specifications implemented to satisfy some of those
requirements.

There are two primary uses for a conformance profile:

In a conformance claim. When included as
part of a conformance claim, a profile generally indicates the "maximum" (most
favorable) set of requirements that are satisfied by the user agent.

In another specification. When included as
part of another specification, a profile generally indicates the "minimum"
(lower bound) set of requirements that must be satisfied as part of conformance
to that specification.

In either case, a
conformance profile identifies a set of requirements derived from a default set according to the following mechanisms,
collectively called conformance profile labels:

The following sections define the default set of requirements, the structure
of a conformance profile, and how to determine the set of requirements
identified by a profile. UAAG 1.0 does not define any (named) conformance
profiles, but rather defines the mechanism for creating them.

The default set of conformance requirements is defined to
be all of the requirements of all of the provisions of all the checkpoints, as
qualified by their normative inclusions and
exclusions and the following normative inclusions and sufficient techniques
that apply across checkpoints.

Except for the checkpoints in guideline 6 that refer to implementation of APIs, the
user agent must satisfy the checkpoint requirements through at least one
mechanism other than an API. Thus,
for most of the requirements in this document, it is not possible to conform by
only making information available through an API (which would be used, for
example, by an assistive technology to provide the missing feature). For
example, checkpoint 9.3 involves
navigation that must be possible through the user interface, not just via an
API. This and other checkpoints involving user control or configuration will
therefore generally be satisfied through features in the user interface or
through configuration files (see the section on
configuration requirements).

In some cases, a checkpoint may apply equally well to content or user agent
features. When it is necessary to remove ambiguity about the scope of a
checkpoint, the checkpoint definition includes one of the following labels:

The user agent may satisfy a content-only requirement with a mechanism that
also involves user agent features. For instance, to satisfy checkpoint 4.7, the user
agent may provide control for all volume, whether the source is content or the
user agent user interface. Similarly, to satisfy checkpoint 3.3, the user
agent may offer a single configuration that turns off blinking in both content
and the user interface.

The user agent may satisfy the configuration requirements of this document
through configuration files (e.g., profiles, initialization files, style
sheets, themes, etc.). For instance, style sheets might be used as a mechanism
to satisfy the highlight and configuration requirements of checkpoint 10.2. Any functionality
that is configurable through a configuration file should also be configurable
through the user agent user interface.
Furthermore, if configuration files may be edited by hand, the user agent
documentation should explain the configuration file format, or refer to an
explanation (a format specification, for example).

For some of the checkpoints in this document (checkpoints 3.3, 5.1, 5.3, and 5.5), configuration is
preferred, but not required to satisfy the checkpoint in some circumstances.
For other checkpoints, configurability may be as important as the functionality
being configured, and is therefore mandatory.

Since this document allows conformance by a user agent consisting of
multiple software components, there are likely to be times when, to satisfy the
configuration requirements of the document, each component has to provide for
configuration independently. To make configuration easier for the user,
components should share and inherit configurations (including those of the
operating environment).

When a user agent runs in more than one operating environment (e.g., a user
agent implemented in Java on top of another operating system), the user agent
may satisfy the relevant requirements (e.g., the checkpoints in guideline 7) of a conformance profile
by following the conventions of a single operating environment.

When faced with a choice between the conventions of different operating
environments, a developer should follow the conventions that benefit
accessibility most, while meeting the developer's design goals. For instance,
some developers may prefer cross-platform consistency over consistency with
other user agents running in a given operating environment, and this might
affect which conventions would be preferred.

Required: A list of requirements (checkpoints or portions of checkpoints)
that do notapply. A conformance
profile should also explain why those requirements do not apply.

Required: Information about one or more specifications (e.g., markup
languages, style sheet languages, APIs, etc.)
implemented to satisfy the requirements of this document. A user agent must
satisfy the requirements identified by the profile for at least these
specifications. A user agent is not required to satisfy the identified
requirements for other implemented specifications except when a content type label definition states otherwise.
The profile must include enough information to identify the implemented
specifications. The profile should indicate which specifications are used to
satisfy which requirements (e.g., which image formats are used to satisfy the
requirements associated with the Image content type label).

A profile should not include other information that the required and
optional assertions. The wording of the profile should reflect whether the
profile is used as part of a conformance claim ("the user agent satisfies these
requirements") or as part of another specification ("the user agent must
satisfy these requirements").

When a profile is part of a conformance claim, the absence of a conformance profile label implies that the
associated requirements are not be satisfied (though the requirements may or
may not actually be satisfied). When a profile is included in another
specification, the absence of a conformance profile
label implies that the associated requirements need not be satisfied.

Thus, a conformance profile when evaluating a user agent might be as short
as:

This content type label refers to all of the requirements related to
visually rendered text for the following checkpoints: 3.3, 4.1, 4.2, and 4.3. If a user agent renders text visually, it must satisfy
these requirements in order to conform. An audio-only or tactile-only user
agent is not required to satisfy the requirements associated with this label.
The user agent must satisfy these requirements for all
implemented formats that produce visually
rendered text, not just those identified in a
conformance profile.

This content type label refers to all of the requirements related to images
(excluding animated images) for the following checkpoints: 3.1 and 3.6. To conform, the user agent
must implement at least one image format. The
user agent must satisfy these requirements for all
implemented image formats, not just those identified in a conformance profile. The image requirements apply
to image content that is
recognized as distinct and that, according to the encoding format, may be
rendered as a coherent unit.

This content type label refers to all of the requirements related to animations (including video and animated
images) for the following checkpoints: 3.2, 4.4,
and 4.5. To conform, the
user agent must implement at least one animation format.
The user agent must satisfy the requirements of checkpoint 3.2 for all implemented animation formats, not just
those identified in a conformance profile. The
animation requirements apply to animation content that is recognized as distinct and that, according
to the encoding format, may be rendered as a coherent unit.

This content type label refers to all of the requirements related to video
for the following checkpoints: 2.5,
2.6, and 3.2. To
conform, the user agent must implement at least one video
format. The user agent must satisfy the requirements of checkpoint 3.2 for all implemented video formats, not just those
identified in a conformance profile. The video
requirements apply to video content that is
recognized as distinct and that, according to the encoding format, may be
rendered as a coherent unit.

This content type label refers to all of the requirements related to audio for the following checkpoints: 2.5, 2.6, 3.2, 4.4, 4.5, 4.7, and 4.8. To conform, the
user agent must implement at least one audio format. The
user agent must satisfy the requirements of checkpoints 3.2 and 4.7 for all implemented audio formats, not just those
identified in a conformance profile. The audio
requirements apply to audio content that is
recognized as distinct and that, according to the encoding format, may be
rendered as a coherent unit.

This content type label refers to all of the requirements related to
synthesized speech for the following checkpoints: 4.9, 4.10, 4.11, 4.12, and 4.13. To conform, the
user agent must support synthesized speech.

Note: As indicated above, some of the content type labels
require implementation of at least one format (e.g., for images). This document
does not require implementation of specific formats, (e.g.,
PNG
[PNG] versus SVG[SVG] for images). However, see the
requirements of checkpoint
8.2.

Some of the content type labels require that certain checkpoints be
satisfied for all implemented specifications, not just those
listed in a conformance profile, in order
to ensure that the goal of the checkpoint is met. For instance, checkpoint 3.3 involves
turning off blinking and animated text. Since there is a risk that these
rendering effects may trigger seizures in people with photosensitive epilepsy,
it is important that the user be able to turn them off in all cases (whether or
not the specification is identified in a conformance profile).

The following checkpoints are designed to augment user agent support for
event-driven behavior specified by the author: 1.2, 9.5, and 9.6. Satisfying these
checkpoints will promote input device independence and thus enable users with
some disabilities to make better use of content designed for a single input
device (generally a pointing device). The Events
label refers to the requirements of these checkpoints.

This document does not require the user agent to implement a selection mechanism in order to conform.
However, if the user agent does implement a selection mechanism, in order to
conform it must satisfy the relevant portions of the following checkpoints: 5.4, 6.6, 7.1, 9.4, 10.2, and 10.3. The Selection label refers to the selection requirements of
these checkpoints.

Each input modality label defines a set of requirements related to support
for a particular type of input device. Input device requirements in this
document are either stated generically (e.g., "input configuration"
requirements) or as keyboard-specific requirements (e.g., "keyboard API").

This input modality label refers to all of the input device requirements of
this document, but applied to pointing device input. For keyboard-specific
requirements, substitute "pointing device input" for "keyboard." The set of
pointing device input requirements does not include the requirements of checkpoint 11.4.

This input modality label refers to all of the input device requirements of
this document, but applied to voice input. For keyboard-specific requirements,
substitute "voice input" for "keyboard." The set of voice input requirements
does not include the requirements of
checkpoint 11.4.

Note: Developers are encouraged to design user agents that
are at least partially operable through pointing device and/or voice input, in
addition to being fully operable through the keyboard.

A checkpoint (or part of a checkpoint) applies unless any one of
the following conditions is met:

The checkpoint makes requirements for graphical user interfaces or
graphical viewports and the user agent only has audio or tactile user
interfaces or viewports.

The checkpoint refers to a role of content (e.g., transcript, captions,
associated conditional
content, synchronization cue, a table element, etc.) that the user agent
cannot recognize because of how the content has
been encoded in a particular format. For instance, HTML user agents can
recognize "alt", OBJECT content, or
NOFRAMES content as specified mechanisms for conditional content. On the other
hand, HTML user agents are not expected to recognize that a nearby paragraph is
a text equivalent for the image (when
not marked up as such).

The checkpoint requires control of a content property that the user agent
cannot recognize because of how the content has
been encoded in a particular format. Some examples of this include:

captioning information that is "burned" into a video presentation and
cannot be recognized as captions in the presentation format;

streamed content that cannot be fast forwarded or rewound;

information encoded in an unrecognized XML namespace;

information or relationships encoded in scripts in a
manner that cannot be recognized. For instance, the requirements of checkpoint 3.3 would not
apply for animation effects unrecognized in a script. Some input device
behavior may be controlled by scripts in a manner that the user agent cannot
recognize. For example, when the author uses event
bubbling to dispatch events, the user agent is not likely to recognize the
full set of elements that may receive those events; the user agent is expected
to recognize which element has the explicitly
associated event handler.

For this profile, we must include VisualText since the user agent renders
text visually.

For this profile, we also wish to include the labels Image, Video, and
Audio, so the user agent must satisfy those requirements as well. Consider the
following checkpoint:

4.4 Slow multimedia.
(P1)

Allow the user to slow the presentation rate of rendered
audio and animation content (including video and
animated images).

As part of satisfying provision one of this checkpoint, for
a visual track, provide at least one
setting between 40% and 60% of the original speed.

As part of satisfying provision one of this checkpoint, for
a prerecorded audio track including audio-only presentations,
provide at least one setting between 75% and 80% of the original speed.

When the user agent allows the user to slow the visual track
of a synchronized multimedia presentation to between 100% and 80% of its
original speed, synchronize the visual and audio tracks (per checkpoint 2.6). Below 80%,
the user agent is not required to render the audio
track.

The second provision is specific to video, so must be satisfied for this
profile. The third provision is specific to audio, so must be satisfied as
well. The fourth provision involves synchronization, but the user agent does
not implement any synchronized multimedia format (see step 6).

Note also the relevant normative exclusions for this checkpoint: the user
agent is not required to satisfy the requirements of this checkpoint for audio
and animations whose recognized role is to create a purely stylistic effect. In
our example, the user agent provides the functionality for all audio and
animations – even those used for purely stylistic effects – even
though this is not required.

Although the user agent implements two animation formats, it only meets
some, but not all, of the requirements associated with the Animation label.
Therefore, we do not include it in the profile.

Information about the user agent. The user agent may consist of one or more
component. For each component, the claim must include the following:

Name and version information for the component. Version information must be
sufficient to identify the user agent (e.g., vendor name, version number, minor
release number, required patches or updates, natural language of the user
interface or documentation). The version information may refer to a range of
user agents (e.g., "this claim refers to all user agents version 6.x").

Name and version information for the operating environment (or
environments) in which the component is running.

Condition 2: At least one version of the claim must conform to the "Web
Content Accessibility Guidelines 1.0" [WCAG10], level A. This claim may
appear on the Web, on a CD-ROM, etc. If a
conformance icon is part of a claim on the Web, it must link to the W3C
explanation of the icon.

This specification imposes no restrictions on the format used to make a well-formed claim. For instance,
the claim may be marked up using HTML (see sample
claim), or expressed in the Resource Description Framework
(RDF) [RDF10].

Here is a sample conformance claim (expressed in
HTML):

<p>On 21 August
2002, UserAgent X (version 2.3) running on MyOperatingSystem (version 4.2)
conforms to <abbr title="the World Wide Web
Consortium">W3C</abbr>'s "User Agent Accessibility Guidelines 1.0",
http://www.w3.org/TR/2002/WD-UAAG10-20020821. Conformance level: Double A.
Supported conformance profile labels: VisualText, Image, Animation, Audio,
Events, and Selection. A <a
href="http://example.com/checkpoints">list</a> of formats used to
satisfy the requirements, and of checkpoints that do not apply is available
online. The specifications that are part of this profile are W3C's HTML 4.0,
CSS2, PNG, and SVG (where each acronym links to the corresponding
specification). </p>

A conformance claim is valid if it is
well-formed and if the user agent satisfies the requirements of the chosen
conformance profile.

The document has been designed to help non-experts evaluate the validity of
conformance claims. Some checkpoints may require interpretation and judgment.
In some cases, although a requirement is clearly stated, without documentation
or feedback from developers (e.g., about implemented APIs) it may
be difficult to evaluate whether a user agent has satisfied the requirement.
Some checkpoints (e.g., those requiring developers to follow conventions or
implement specifications defined outside this document) are inherently more
open to interpretation than others.

It is not currently possible to evaluate the validity of a claim
automatically.

User agents do not conform to this document on a per-resource basis; claims
are not as specific as "the user agent conforms for this particular Web page."
A claim is valid if the user agent satisfies the requirements identified by the
claim for most general-purpose content, in ordinary operating conditions.

In some cases, the author's content may limit the user agent's functionality
for specific reasons, such as to protect intellectual property rights, to
provide a read-only view (allowing no user interaction), or to limit
interaction for a specialized purpose (e.g., a "written" driving test). Content
that limits the functionality of the user agent in some cases does not
automatically invalidate a claim about the user agent.

A conformance claim (with or without an accompanying conformance icon) is an assertion that a user
agent has satisfied the requirements of a chosen conformance profile. Claimants
(or relevant assuring parties) are solely responsible for the validity of their
claims, keeping claims up to date, and proper use of the conformance icons.

The existence of a conformance claim (with or without an accompanying
conformance icon) does not imply that W3C has reviewed the claim or assured its
validity. As of the publication of this document, W3C does not act as an
assuring party, but it may do so in the future, or it may establish
recommendations for assuring parties.

Claimants are expected to modify or retract a claim if it may be
demonstrated that the claim is not valid. Claimants are encouraged to claim
conformance to the most recent User Agent Accessibility Guidelines
Recommendation available.

This specification imposes no restrictions about:

who may make a claim (e.g., vendors about their own user agents, third
parties about those user agents, journalists about user agents, etc.),
or

where claims may be published (e.g., on the Web or in paper
documentation).

People may use a conformance icon (or, "conformance logo") on a Web site, on
user agent packaging, in documentation, etc. It is meaningless to use a
conformance icon on its own, i.e., to use the icon without an associated well-formed claim.

Draft Note:In the event this document becomes a W3C
Recommendation this document will link to the W3C Web site for additional
information about the icons and how to use them.

Authors of technical specifications (such as W3C Recommendations) should
incorporate the requirements of UAAG 1.0 as part of conformance to their
specifications. This may be done by direct
inclusion, or by reference using a conformance profile. Direct inclusion promotes
the integration of specialized accessibility requirements; inclusion by
reference is easier and less prone to error.

Identify accessibility features of the specification where they are defined
(see checkpoint
8.1). Optionally, create an appendix of these accessibility features as
well.

Remember to include user interface requirements as part of conformance to
the specification. Authors of technical specifications tend to focus more on
the rendering process or other content-related behavior, and less on user
interface requirements. UAAG 1.0 makes a number of user interface requirements
that authors will need to consider (such as those in guideline 5 pertaining to
viewport behavior).

Include at least an informative reference to UAAG 1.0 and Techniques for
UAAG 1.0. See the section on how to refer to UAAG
1.0 for more information.

Consult the User Agent Accessibility Guidelines Working Group when a
question arises about how a checkpoint applies for a technology, such as
whether a term is used differently between UAAG 1.0 and the technical
specification.

For more information on designing specifications that promote accessibility,
refer to W3C's "XML Accessibility Guidelines" [XAG10].

Rather than including the generic UAAG 1.0 requirements, tailor them to the
specification. Be specific in the requirements, and include (in context) a
reference to the original UAAG 1.0 checkpoint. The following examples
illustrate what is meant by direct inclusion:

In an HTML specification, where the script,
applet, and object elements are defined, include a
statement such as "Per checkpoint 3.4 of UAAG 1.0, a conforming user agent must
allow configuration not to execute scripts, applets, or other executable
content."

In a CSS specification, where the 'text-decoration' property
is defined, include a statement such as "A conforming user agent must either:
(a) allow configuration to override the 'blink' value with the
'none' value, or (b) ignore the 'blink' value. This is required by
checkpoint 3.3 of UAAG
1.0 [UAAG10]."

Note how these examples refer to the specific elements, attributes, properties,
etc., of the specifications.

It is better to include some UAAG 1.0 requirements in a specification than
no UAAG 1.0 requirements. However, since UAAG 1.0 requirements are designed to
complement one another, arbitrary selection of requirements may result in
accessibility gaps. Authors should include requirements according to the groups
defined by the conformance profile labels.

Additionally, an authoring tool which is a Conforming SVG Generator conforms
to all of the Priority 1 accessibility guidelines from the document "Authoring
Tool Accessibility Guidelines 1.0" that are relevant to generators of SVG
content.

This statement requires conformance to the Authoring Tool Accessibility
Guidelines as part of conformance to SVG 1.0 (for certain classes of tools).
This type of "conformance requirement by reference" is also possible for UAAG
1.0, by inclusion of a conformance
profile.

The following is a (partial) example of a conformance profile for the
MyFormat specification (expressed in plain text):

As part of conformance to MyFormat 1.0, a user agent must satisfy the
following conformance profile:

This glossary is normative. However, some
terms (or parts of explanations of terms) may not have an impact on
conformance.

Note: In this document, glossary terms generally link to
the corresponding entries in this section. These terms are also highlighted
through style sheets and identified as glossary terms through markup.

The effect of activation depends on the type of the user interface control. For
instance, when a link is activated, the user agent generally retrieves the
linked Web resource. When a form element is
activated, it may change state (e.g., check boxes) or may take user input
(e.g., a text entry field).

In this document, "to alert" means to make the user aware
of some event, without requiring acknowledgement. For example, the user agent
may alert the user that new content is available on the server by displaying a
text message in the user agent's status bar. See
checkpoint 1.3 for requirements
about alerts.

In this document, an "animation" refers to content that, when rendered, creates a visual
movement effect automatically (i.e., without manual user interaction). This
definition of animation includes video and animated images. Animation
techniques include:

graphically displaying a sequence of snapshots within the same region
(e.g., as is done for video and animated images). The series of snapshots may
be provided by a single resource (e.g., an animated GIF image) or from distinct
resources (e.g., a series of images downloaded continuously by the user
agent).

scrolling text (e.g., achieved through markup or style sheets).

displacing graphical objects around the viewport (e.g., a picture of a ball
that is moved around the viewport giving the impression that it is bouncing off
of the viewport edges). For instance, the SMIL 2.0 [SMIL20] animation modules explain
how to create such animation effects in a declarative manner (i.e., not by
composition of successive snapshots).

An application programming interface (API) defines how
communication may take place between applications.

Implementing APIs that are independent of a particular operating environment
(as are the W3C DOM Level 2 specifications) may reduce implementation costs for
multi-platform user agents and promote the development of multi-platform
assistive technologies. Implementing conventional APIs for a particular
operating environment may reduce implementation costs for assistive technology
developers who wish to interoperate with more than one piece of software
running on that operating environment.

A "device API" defines how communication may take place
with an input or output device such as a keyboard, mouse, video card, etc.

In this document, an "input/output API" defines how
applications or devices communicate with a user agent. As used in this
document, input and output APIs include, but are not limited to, device APIs.
Input and output APIs also include more abstract communication interfaces than
those specified by device APIs. A "conventional input/output API" is one that
is expected to be implemented by software running on a particular operating
environment. For example, on desktop computers today, the conventional input
APIs are for the mouse and keyboard. For touch screen
devices or mobile devices, conventional input APIs may
include stylus, buttons, voice, etc. The graphical display and sound card are
considered conventional output devices for a graphical desktop computer
environment, and each has an associated API.

In the context of this document, an assistive technology
is a user agent that:

relies on services (such as retrieving Web
resources, parsing markup, etc.) provided by one or more other "host" user
agents. Assistive technologies communicate data and messages with host user
agents by using and monitoring
APIs.

For example, screen reader software is an assistive technology because it
relies on browsers or other software to enable Web access, particularly for
people with visual and learning disabilities.

Examples of assistive technologies that are important in the context of this
document include the following:

screen magnifiers, which are used by people with visual disabilities to
enlarge and change colors on the screen to improve the visual readability of
rendered text and images.

screen readers, which are used by people who are blind or have reading
disabilities to read textual information through synthesized speech or braille
displays.

voice recognition software, which may be used by people who have some
physical disabilities.

alternative keyboards, which are used by people with certain physical
disabilities to simulate the keyboard.

alternative pointing devices, which are used by people with certain
physical disabilities to simulate mouse pointing and button activations.

Beyond this document, assistive technologies consist of
software or hardware that has been specifically designed to assist people with
disabilities in carrying out daily activities, e.g., wheelchairs, reading
machines, devices for grasping, text telephones, vibrating pagers, etc. For
example, the following very general definition of "assistive technology device"
comes from the (U.S.) Assistive Technology Act of 1998 [AT1998]:

Any item, piece of equipment, or product system, whether acquired
commercially, modified, or customized, that is used to increase, maintain, or
improve functional capabilities of individuals with disabilities.

An audio-only presentation is content consisting
exclusively of one or more audio tracks presented
concurrently or in series. Examples of an audio-only presentation include a
musical performance, a radio-style news broadcast, and a narration.

An audio object is content rendered as sound through an
audio viewport. An audio track is an audio object
that is intended as a whole or partial presentation. An audio track may, but is
not required to, correspond to a single audio channel (left or right audio
channel).

An audio description (called an "auditory description" in
the Web Content Accessibility Guidelines 1.0 [WCAG10]) is either a prerecorded
human voice or a synthesized voice (recorded or generated dynamically)
describing the key visual elements of a movie or other animation. The audio
description is synchronized with (and possibly included
as part of) the audio track of the presentation, usually
during natural pauses in the audio track. Audio
descriptions include information about actions, body language, graphics, and
scene changes.

Captions are text transcripts that are synchronized with other audio tracks or
visual tracks. Captions convey information about spoken words and
non-spoken sounds such as sound effects. They benefit people who are deaf or
hard-of-hearing, and anyone who cannot hear the audio (e.g., someone in a noisy
environment). Captions are generally rendered
graphically superimposed ("on top of") the synchronized visual track.

The term "open captions" generally refers to captions that are always
rendered with a visual track; they cannot be turned off. The term "closed
captions" generally refers to captions that may be turned on and off. The
captions requirements of this document assume that the user agent can recognize the captions as such; see the
section on applicability for more information.

Note: Other terms that include the word "caption" may have
different meanings in this document. For instance, a "table caption" is a title
for the table, often positioned graphically above or below the table. In this
document, the intended meaning of "caption" will be clear from context.

A "character encoding" is a mapping from a character set
definition to the actual code units used to represent the data. Refer to the
Unicode specification [UNICODE] for more information
about character encodings. Refer to "Character Model for the World Wide Web"
[CHARMOD] for additional information about characters and character
encodings.

A collated text transcript is a text
equivalent of a movie or other animation. More specifically, it is the
combination of the text transcript of the
audio track and the text equivalent of
the visual track. For example, a collated
text transcript typically includes segments of spoken dialogue interspersed
with text descriptions of the key visual elements of a presentation (actions,
body language, graphics, and scene changes). See also the definitions of text transcript and audio description. Collated text
transcripts are essential for individuals who are deaf-blind.

Conditional content is content that, by format
specification, should be made available to users through the user interface,
generally under certain conditions (e.g., based on user preferences or
operating environment limitations). Some examples of conditional content
mechanisms include:

The "alt" attribute of the IMG element in HTML 4.
According to
section 13.2 of the HTML 4 specification ([HTML4]): "User agents must render
alternate text when they cannot support images, they cannot support a certain
image type or when they are configured not to display images.

The switch element and test attributes in SMIL 1.0. Sections
4.3 and 4.4, respectively,
of SMIL 1.0
[SMIL] explain the conditional rendering rules of these
features.

SVG 1.0
[SVG] also includes a switch element and several
attributes for conditional processing.

The NOSCRIPT and NOFRAMES elements in HTML 4
[HTML4]
allow the author to provide content under conditions when the user agent does
not support scripts or frames, or the user has turned off support for scripts
or frames.

Specifications vary in how completely they define how and when to render
conditional content. For instance, the HTML 4 specification includes the
rendering conditions for the "alt" attribute, but not for the
"title" attribute. The HTML 4 specification does indicate that the
"title" attribute should be available to users through the user
interface ("Values of the title attribute may be rendered by user agents in a
variety of ways...").

Note: The Web Content Accessibility Guidelines 1.0 requires
that authors provide text equivalents for non-text content. This is generally
done by using the conditional content mechanisms of a markup language. Since
conditional content may not be rendered by default, the current document
requires the user agent to provide access to unrendered conditional content (checkpoint 2.3 and checkpoint 2.9)
as it may have been provided to promote accessibility.

In the context of this document, the verbs "to control"
and "to configure" share in common the idea of governance such as a user may
exercise over interface layout, user agent behavior, rendering style, and other
parameters required by this document. Generally, the difference in the terms
centers on the idea of persistence. When a user makes a change by
"controlling" a setting, that change usually does not persist beyond that user
session. On the other hand, when a user "configures" a setting, that setting
typically persists into later user sessions. Furthermore, the term "control"
typically means that the change can be made easily (such as through a keyboard
shortcut) and that the results of the change occur immediately. The term
"configure" typically means that making the change requires more time and
effort (such as making the change via a series of menus leading to a dialog
box, via style sheets or scripts, etc.). The results of "configuration" might
not take effect immediately (e.g., due to time spent reinitializing the system,
initiating a new session, rebooting the system).

In order to be able to configure and control the user agent, the user needs
to be able to "write" as well as "read" values for these parameters.
Configuration settings may be stored in a profile.
The range and granularity of the changes that can be controlled or configured
by the user may depend on limitations of the operating environment or
hardware.

Both configuration and control may apply at different "levels": across Web resources (i.e., at the user agent
level, or inherited from the operating environment), to the
entirety of a Web resource, or to components of a Web resource (e.g., on a
per-element basis).

A
global configuration is one that applies across elements of the
same Web resource, as well as across Web resources. A global configuration may
be implemented by more than one setting (e.g., per component of the user
agent). For instance, when a user agent consists of a browser that renders HTML
and a plug-in that renders SVG, to satisfy the global configuration
requirements of this document, the browser may provide one setting and the
plug-in another.

User agents may allow users to choose configurations based on various
parameters, such as hardware capabilities, natural language, etc.

It is used to mean the content of an HTML or XML element, in the sense
employed by the XML 1.0 specification ([XML], section 3.1): "The text between
the start-tag and end-tag is called the element's content." Context should
indicate that the term content is being used in this sense.

Empty
content (which may be conditional content) is either a
null value or an empty string (i.e., one that is zero characters long). For
instance, in HTML, alt="" sets the value of the "alt"
attribute to the empty string. In some markup languages, an element may have
empty content (e.g., the HR element in HTML).

In general usage, the term "document object" refers to the user agent's
representation of data (e.g., a document). This data generally comes from the
document source, but may also be
generated (from style sheets, scripts, transformations, etc.), produced as a
result of preferences set within the user agent, added as the result of a
repair performed automatically by the user agent, etc. Some data that is part
of the document object is routinely rendered (e.g., in HTML, what
appears between the start and end tags of elements and the values of attributes
such as "alt", "title", and "summary"). Other parts of the document object are
generally processed by the user agent without user awareness, such as DTD- or schema-defined names of
element types and attributes, and other attribute values such as "href", "id",
etc. These guidelines require that users have access to both kinds of data
through the user interface. Most of the requirements of this document apply to
the document object after its construction. However, a few checkpoints (e.g.,
checkpoint 2.7 and checkpoint 2.10) may
affect the construction of the document object.

A "document object model" is the abstraction that governs the construction
of the user agent's document object. The document object model employed by
different user agents may vary in implementation and sometimes in scope. This
specification requires that user agents implement the APIs defined
in Document Object Model (DOM) Level 2 specifications ([DOM2CORE]
and
[DOM2STYLE]) for access to HTML,
XML, and CSS content. These DOM APIs allow authors
to access and modify the content via a scripting language (e.g., JavaScript) in
a consistent manner across different scripting languages. As a standard
interface, the DOM APIs make it easier not just for authors, but for assistive
technology developers to extract information and render it in ways most suited
to the needs of particular users.

A document character set (a concept taken from SGML) is a
sequence of abstract characters that may appear in Web content represented in a
particular format (such as HTML, XML, etc.). A document character set consists
of:

A "repertoire": A set of abstract characters, such as the Latin letter "A",
the Cyrillic letter "I", the Chinese character meaning "water", etc.

Code positions: A set of integer references to characters in the
repertoire.

For instance, the character set required by the HTML 4 specification [HTML4] is defined
in the Unicode specification [UNICODE]. Refer to "Character
Model for the World Wide Web" [CHARMOD] for more information
about document character sets.

In this document, the term "document source" refers to the
data that the user agent receives as the direct result of a request for a Web resource (e.g., as the result of an
HTTP/1.1
[RFC2616] "GET", or as the result of viewing a resource on the local
file system). The document source generally refers to the "payload" of the user
agent's request, and does not generally include information exchanged as part
of the transfer protocol. The document source is data that is prior to any
repair by the user agent (e.g., prior to repairing invalid markup). "Text
source" refers to document source that is composed of text.

Documentation refers to information that supports the use
of a user agent. This information may be found in manuals, installation
instructions, the help system, tutorials, etc. Documentation may be distributed
(e.g., some parts may be delivered on CD-ROM, others on the Web). Refer to guideline 12 for information about
documentation requirements.

This document uses the terms "element" and "element type"
in the sense employed by the XML 1.0 specification ([XML], section 3): an element type is
a syntactic construct of a document type definition (DTD) for its application.
This sense is also relevant to structures defined by XML schemas. The document
also uses the term "element" more generally to mean a type of content (such as
video or sound) or a logical construct (such as a header or list).

An enabled element is a piece of content
with associated behaviors that may be activated through the user interface or
through an API. The set
of elements that a user agent enables is generally derived from, but is not
limited to, the set of interactive
elements defined by implemented markup languages.

Some elements may only be enabled elements for part of a user session. For
instance, an element may be disabled by a script as the result of user
interaction. Or, an element may only be enabled during a given time period
(e.g., during part of a SMIL 1.0 [SMIL] presentation). Or, the user
may be viewing content in "read-only" mode, which may disable some
elements.

A disabled element is a piece of content that is potentially an
enabled element, but is not in the current session. One example of a disabled
element is a menu item that is unavailable in the current session; it might be
"greyed out" to show that it is disabled. Generally, disabled elements will be
interactive elements that are not
enabled in the current session. This document distinguishes disabled elements
(not currently enabled) from non-interactive elements (never enabled).

For the requirements of this document, user
selection does not constitute user interaction with enabled elements. See
the definition of content focus.

Note: The term "active element" is not used in this
document since it may suggest several different concepts, including:
interactive element, enabled element, an element "in the process of being
activated" (which is the meaning of ':active' in CSS2 [CSS2], for example).

The term "equivalent" is used in this document as it is
used in the Web Content Accessibility Guidelines 1.0 [WCAG10]:

Content is "equivalent" to other content when both fulfill essentially the
same function or purpose upon presentation to the user. In the context of this
document, the equivalent must fulfill essentially the same function for the
person with a disability (at least insofar as is feasible, given the nature of
the disability and the state of technology), as the primary content does for
the person without any disability.

Equivalents include text equivalents
(e.g., text equivalents for images, text transcripts for audio tracks, or
collated text transcripts for a movie) and non-text equivalents (e.g., a
prerecorded audio description of a
visual track of a movie, or a sign language video rendition of a written
text).

Each markup language defines its own mechanisms for specifying conditional content, and these
mechanisms may be used by authors to provide text equivalents. For instance, in
HTML 4
[HTML4] or SMIL 1.0 [SMIL], authors may use the
"alt" attribute to specify a text equivalent for some elements. In
HTML 4, authors may provide equivalents and other conditional content in
attribute values (e.g., the "summary" attribute for the TABLE
element), in element content (e.g., OBJECT for external content it
specifies, NOFRAMES for frame equivalents, and
NOSCRIPT for script equivalents), and in prose. Please consult the Web
Content Accessibility Guidelines 1.0 [WCAG10] and its associated
Techniques document [WCAG10-TECHS] for more
information about equivalents.

User agents often perform a task when an event having a
particular "event type" occurs, including user interface, changes to content,
loading of content, a request from the operating environment, etc.
Some markup languages allow authors to specify that a script, called an event
handler, be executed when an event of a given type occurs. An
event handler is explicitly associated with an element when the event handler
is associated with that element through markup or the DOM.
The term "event bubbling"
describes a programming style where a single event handler dispatches events to
more than one element. In this case, the event handlers are not explicitly
associated with the elements receiving the events (except for the single
element that dispatches the events).

Note: The combination of HTML, style sheets, the Document
Object Model (DOM), and scripting is commonly referred to as
"Dynamic HTML" or DHTML. However, as there is no W3C specification that
formally defines DHTML, this document only refers to event handlers and
scripts.

Some examples of explicit user requests include when the user selects "New
viewport", responds "Yes" to a prompt in the user agent's user interface,
configures the user agent to behave in a certain way, or changes the selection
or focus with the keyboard or pointing device.

Note: Users make mistakes. For example, a user may
inadvertently respond "yes" to a prompt when they meant "no." In this document,
this type of mistake is still considered an explicit user request.

In this document, the term "content focus" (required by checkpoint 9.1) refers to a
user agent mechanism that has all of the following properties:

It designates zero or one element in content
that is either enabled or disabled. In general, the focus
should only designate enabled elements, but it may also designate disabled
elements.

It has state: the user may "set it" (programmatically or through the user
interface) on an enabled element.
Events may be triggered when the focus is set (or unset). Which events are
triggered depends on the content (e.g., HTML events and CSS pseudo-classes) or
user interface settings.

Once it has been set, it may be used to trigger other behaviors associated
with the enabled element (e.g., the user may activate a link or change the
state of a form control). These behaviors may be triggered programmatically or
through the user interface (e.g., through keyboard events).

User interface mechanisms may resemble content focus, but do not satisfy all
of the properties. For example, text editors often implement a "caret" that
indicates the current location of text input or editing. The caret may have
state and may respond to input device events, but it does not enable users to
activate the behaviors associated with enabled elements.

The user interface focus shares the properties of the content focus except
that, rather than designating pieces of content, it designates zero or one control of the user agent user interface
that has associated behaviors (e.g., radio button, text box, menu, etc.).

On the screen, the content focus may be
highlighted using colors, fonts, graphics, magnification, etc. The content
focus may also be highlighted when rendered as synthesized speech, for example
through changes in speech prosody. The
dimensions of the rendered content focus may exceed those of the
viewport.

In this document, each viewport is expected to have at most one content
focus and at most one user interface focus. This document includes requirements
for content focus only, for user interface focus only, and for both. When a
requirement refers to both, the term "focus" is used.

When several viewports coexist, at most one viewport's
content focus or user interface focus responds to input
events; this is called the current focus.

This document uses the term "image" to refer (as is
commonly the case) to pictorial content. However, in this
document, term image is limited to static (i.e., unmoving) visual information.
See also the definition of animation.

An input configuration is the set of "bindings" between
user agent functionalities and
user interface input mechanisms (e.g., menus, buttons, keyboard keys, voice
commands, etc.). The default input configuration is the set of bindings the
user finds after installation of the software; it must be documented (per checkpoint 12.3]). Input
configurations may be affected by author-specified bindings (e.g., through the
"accesskey" attribute of HTML 4 [HTML4]).

An interactive element is piece of content that, by
specification, may have associated behaviors to be executed or carried out as a
result of user or programmatic interaction. For instance, the interactive
elements of HTML 4 [HTML4] include: links, image maps,
form elements, elements with a value for the "longdesc" attribute, and elements
with event handlers explicitly associated
with them (e.g., through the various "on" attributes). The role of an element
as an interactive element is subject to
applicability. A non-interactive element is an element that, by format
specification, does not have associated behaviors. The expectation of this
document is that interactive elements become enabled elements in some sessions,
and non-interactive elements never become enabled elements.

What is identified as "normative" is required for conformance (noting that one may conform in a variety
of well-defined ways to this document). What is identified as "informative"
(sometimes, "non-normative") is never required for conformance.

In this document, the term "override" means that one
configuration or behavior preference prevails over another. Generally, the
requirements of this document involve user preferences prevailing over author
preferences and user agent default settings and behaviors. Preferences may be
multi-valued in general (e.g., the user prefers blue over red or yellow), and
include the special case of two values (e.g., turn on or off blinking text
content).

A placeholder is content generated by the user agent to
replace author-supplied content. A placeholder may be generated as the result
of a user preference (e.g., to not render images) or as
repair content (e.g., when an image cannot be found). Placeholders can be
any type of content, including text, images, and audio cues.

This document includes requirements that the user be able to view the
original author-supplied content associated with a placeholder. To satisfy
these requirements, the user agent might render the content in place of the
placeholder or in a separate viewport (leaving the placeholder as is). A
request to view the original content associated with a
placeholder is considered an explicit user request to render
that content.

This document does not require user agents to include placeholders in the document object. A placeholder that
is inserted in the document object should conform to the Web Content
Accessibility Guidelines 1.0 [WCAG10]. If a placeholder is not
part of the document object, it is part of the user interface only (and
subject, for example, to checkpoint
1.3).

The point of regard is a position in rendered content that the user is
presumed to be viewing. The dimensions of the point of regard may vary. For
example, it may be a point (e.g., a moment in an audio rendering or a cursor in
a graphical rendering), or a range of text (e.g., focused text), or a
two-dimensional area (e.g., content rendered through a two-dimensional
graphical viewport). The point of regard is almost always within the viewport,
but it may exceed the spatial or temporal
dimensions of the viewport (see the definition of rendered content for more
information about viewport dimensions). The point of regard may also refer to a
particular moment in time for content that changes over time (e.g., an audio-only presentation).
User agents may determine the point of regard in a number of ways, including
based on viewport position in content,
content focus, selection, etc. A user agent should not
change the point of regard unexpectedly as this may disorient the user. The
point of regard should be available programmatically (e.g., for assistive
technologies).

A profile is a named and persistent representation of user preferences that
may be used to configure a user agent. Preferences include input
configurations, style preferences, natural language preferences, etc. In operating environments with
distinct user accounts, profiles enable users to reconfigure software quickly
when they log on, and profiles may be shared by several users.
Platform-independent profiles are useful for those who use the same user agent
on different platforms.

In this document, "to prompt" means to require input from
the user. The user agent should allow users to
configure how they wish to be prompted. For instance, for a user agent
functionality X, configurations might include: always prompt me before doing X,
always do X without prompting me, never do X but tell me when you could have,
never do X and never tell me that you could have, etc.

A user agent renders a document by applying formatting
algorithms and style information to the document's elements. Formatting depends
on a number of factors, including where the document is rendered: on screen, on
paper, through loudspeakers, on a braille display, on a mobile device, etc.
Style information (e.g., fonts, colors, synthesized speech prosody, etc.) may
come from the elements themselves (e.g., certain font and phrase elements in
HTML), from style sheets, or from user agent settings. For the purposes of
these guidelines, each formatting or style option is governed by a property and
each property may take one value from a set of legal values. Generally in this
document, the term "property"
has the meaning defined in CSS 2 ([CSS2], section 3). A reference to
"styles" in this document means a set of style-related properties.

The value given to a property by a user agent when it is
installed is called the property's
default value.

Authors encode information in markup languages, style
sheet languages, scripting languages, protocols, etc. When the information is
encoded in a manner that allows the user agent to process it with certainty,
the user agent can "recognize" the information. For instance, HTML allows
authors to specify a heading with the H1 element, so a user agent that
implements HTML can recognize that content as a heading. If the author creates
headings using a visual effect alone (e.g., by increasing the font size), then
the author has encoded the heading in a manner that does not allow the user
agent to recognize it as a heading.

Some requirements of this document depend on content roles, content
relationships, timing relationships, and other information supplied by the
author. These requirements only apply when the author
has encoded that information in a manner that the user agent can recognize. See
the section on conformance for more information
about applicability.

In practice, user agents will rely heavily on information that the author
has encoded in a markup language or style sheet language. On the other hand,
behaviors, style, meaning encoded in a script, and
markup in an unfamiliar XML namespace may not be recognized by the user agent
as easily or at all. The Techniques document [UAAG10-TECHS] lists some
markup known to affect accessibility that user agents can recognize.

Rendered content is the part of content
that the user agent makes available to the user's senses of sight and hearing
(and only those senses for the purposes of this document). Any content that
causes an effect that may be perceived through these senses constitutes
rendered content. This includes text characters, images, style sheets, scripts,
and anything else in content that, once processed, may be perceived through
sight and hearing.

The term "rendered text" refers to text content that is rendered in
a way that communicates information about the characters themselves, whether
visually or as synthesized speech.

In the context of this document, invisible content is content
that influences graphical rendering of other content but is not rendered
itself. Similarly, silent content is content that influences audio rendering of
other content but is not rendered itself. Neither invisible nor silent content
is considered rendered content.

In this document, the term "repair content" refers to
content generated by the user agent in order to correct an error condition.
"Repair text" means repair content consisting only of text. Some error
conditions that may lead to the generation of repair content include:

Missing resources for handling or rendering content (e.g., the user agent
lacks a font family to display some characters, the user agent does not
implement a particular scripting language).

This document does not require user agents to include repair content in the
document object. Repair content
inserted in the document object should conform to the Web Content Accessibility
Guidelines 1.0
[WCAG10]. For more information about repair techniques for Web
content and software, refer to "Techniques for Authoring Tool Accessibility
Guidelines 1.0" [ATAG10-TECHS].

In this document, the term "script" almost always refers to a scripting
(programming) language used to create dynamic Web content. However, in
checkpoints referring to the written (natural) language of content, the term
"script" is used as in Unicode [UNICODE] to mean "A collection of
symbols used to represent textual information in one or more writing systems."

Information encoded in scripts may be difficult for a user agent to recognize. For instance, a user agent is
not expected to recognize that, when executed, a script will calculate a
factorial. The user agent will be able to recognize some information in a
script by virtue of implementing the scripting language or a known program
library (e.g., the user agent is expected to recognize when a script will open
a viewport or retrieve a resource from the Web).

In this document, the term "selection" refers to a user
agent mechanism for identifying a range of content
(e.g., text, images, etc.). Generally, user agents limit selection to text
content (e.g., one or more fragments of text). The
selection may be structured (based on the document tree) or unstructured
(e.g., text-based). The range may be empty.

On the screen, the selection may be
highlighted using colors, fonts, graphics, magnification, etc. The
selection may also be highlighted when rendered as synthesized speech, for
example through changes in speech prosody. The dimensions of the rendered
selection may exceed those of the viewport.

The selection may be used for a variety of purposes: for cut and paste
operations, to designate a specific element in a document for the purposes of a
query, as an indication of point of regard,
etc.

The selection has state, and the user may "set it" (programmatically or
through the user interface).

In this document, each viewport is expected to have at most one selection.
When several viewports coexist, at most one viewport's
selection responds to input events; this is called the current selection.

Note: Some user agents may also implement a selection for
designating a range of information in the user agent user interface.
The current document only includes requirements for a content
selection mechanism.

In this document, the expression "serial access" refers to
one-dimensional access to rendered content.
Some examples of serial access include listening to an audio stream or watching
a video (both of which involve one temporal dimension), or reading a series of
lines of braille one line at a time (one spatial dimension). Many users with
blindness have serial access to content rendered as audio, synthesized speech,
or lines of braille.

The expression "sequential navigation" refers to navigation through an
ordered set of items (e.g., the enabled elements in a document, a
sequence of lines or pages, or a sequence of menu options). Sequential
navigation implies that the user cannot skip directly from one member of the
set to another, in contrast to direct or structured navigation (see guideline 9 for information about
these types of navigation). Users with blindness or some users with a physical
disability may navigate content sequentially (e.g., by navigating through
links, one by one, in a graphical viewport with or without the aid of an
assistive technology). Sequential navigation is important to users who cannot
scan rendered content visually for context and also benefits users unfamiliar
with content. The increments of sequential navigation may be determined by a
number of factors, including element type (e.g., links only), content structure
(e.g., navigation from heading to heading), and the current navigation context
(e.g., having navigated to a table, allow navigation among the table
cells).

Users with serial access to content or who navigate sequentially may require
more time to access content than users who use direct or structured
navigation.

In this document, the terms "support", "implement", and
"conform" all refer to what a developer has designed a user agent to do, but
they represent different degrees of specificity. A user agent "supports"
general classes of objects, such as "images" or "Japanese". A user agent
"implements" a specification (e.g., the PNG and SVG image format
specifications, a particular scripting language, etc.), or an API (e.g.,
the DOM API) when it has been programmed to follow all or part of a
specification. A user agent "conforms to" a specification when it implements
the specification and satisfies its conformance criteria. This
document includes some conformance requirements to other specifications (e.g.,
to a particular level of the "Web Content Accessibility Guidelines 1.0"
[WCAG10]).

In this document, "to synchronize" refers to the act of
time-coordinating two or more presentation components (e.g., in a multimedia
presentation, a visual track with captions). For Web
content developers, the requirement to synchronize means to provide the data
that will permit sensible time-coordinated rendering by a user agent. For
example, Web content developers can ensure that the segments of caption text
are neither too long nor too short, and that they map to segments of the visual
track that are appropriate in length. For user agent developers, the
requirement to synchronize means to present the content in a sensible
time-coordinated fashion under a wide range of circumstances including
technology constraints (e.g., small text-only displays), user limitations (slow
reading speeds, large font sizes, high need for review or repeat functions),
and content that is sub-optimal in terms of accessibility.

As used in this document a "text element" adds text characters to either content or the
user interface. Both in the Web Content Accessibility Guidelines 1.0 [WCAG10] and
in this document, text elements are presumed to produce text that can be
understood when rendered visually, as synthesized speech, or as Braille. Such
text elements benefit at least these three groups of users:

visually-displayed text benefits users who are deaf and adept in reading
visually-displayed text;

synthesized speech benefits users who are blind and adept in use of
synthesized speech;

braille benefits users who are blind, and possibly deaf-blind, and adept at
reading braille.

A text element may consist of both text and non-text data. For instance, a
text element may contain markup for style (e.g., font size or color), structure
(e.g., heading levels), and other semantics. The essential function of the text
element should be retained even if style information happens to be lost in
rendering.

A user agent may have to process a text element in order to have access to
the text characters. For instance, a text element may consist of markup, it may
be encrypted or compressed, or it may include embedded text in a binary format
(e.g., JPEG).

"Text content" is content that is composed of one or more text elements. A
"text equivalent" (whether in content or the user interface) is an equivalent composed of one
or more text elements. Authors generally provide text equivalents for content
by using the conditional
content mechanisms of a specification.

A "non-text element" is an element (in content or the user interface) that
does not have the qualities of a text element. "Non-text content" is composed
of one or more non-text elements. A "non-text equivalent" (whether in content
or the user interface) is an equivalent
composed of one or more non-text elements.

In this document, a "text decoration" is any stylistic effect that the user
agent may apply to visually rendered text that does
not affect the layout of the document (i.e., does not require reformatting when
applied or removed). Text decoration mechanisms include underline, overline,
and strike-through.

A text transcript is a text equivalent of audio
information (e.g., an audio-only presentation or
the audio track of a movie or other
animation). It provides text for both spoken words and non-spoken sounds such
as sound effects. Text transcripts make audio information accessible to people
who have hearing disabilities and to people who cannot play the audio. Text
transcripts are usually created by hand but may be generated on the fly (e.g.,
by voice-to-text converters). See also the definitions of captions and collated text
transcripts.

The software and documentation components that together, conform to the requirements of this document. This is
the most common use of the term in this document and is the usage in the
checkpoints.

Any software that retrieves and renders Web content for users. This may
include Web browsers, media players, plug-ins,
and other programs – including assistive technologies -- that
help in retrieving and rendering Web content.

User agent default styles are style property
values applied in the absence of any author or user styles. Some markup
languages specify a default rendering for documents in that markup language.
Other specifications may not specify default styles. For example,
XML 1.0
[XML] does not specify default styles for XML documents.
HTML 4
[HTML4] does not specify default styles for HTML documents, but the
CSS 2
[CSS2] specification suggests a sample default
style sheet for HTML 4 based on current practice.

the user agent user
interface, i.e., the controls (e.g., menus, buttons, prompts, and
other components for input and output) and mechanisms (e.g., selection and
focus) provided by the user agent ("out of the box") that are not created by content.

the "content user interface", i.e., the enabled elements that are part of
content, such as form controls, links, applets,
etc.

The user agent renders content through one or more
viewports. Viewports include windows, frames, pieces of paper, loudspeakers,
virtual magnifying glasses, etc. A viewport may contain another viewport (e.g.,
nested frames). User agent user interface
controls such as prompts, menus, alerts, etc., are not viewports.

Graphical and tactile viewports have two spatial dimensions. A
viewport may also have temporal dimensions, for instance when audio, speech,
animations, and movies are rendered. When the dimensions (spatial or temporal)
of rendered content exceed the dimensions of the viewport, the user agent
provides mechanisms such as scroll bars and advance and rewind controls so that
the user can access the rendered content "outside" the viewport. Examples
include: when the user can only view a portion of a large document through a
small graphical viewport, or when audio content has already been played.

When several viewports coexist, only one has the
current focus at a given moment. This viewport is
highlighted to make it stand out.

User agents may render the same content in a variety of ways; each rendering
is called a view. For
instance, a user agent may allow users to view an entire document or just a
list of the document's headers. These are two different views of the
document.

A visual object is content rendered through a graphical viewport. Visual objects include graphics,
text, and visual portions of movies and other animations. A visual track is a
visual object that is intended as a whole or partial presentation. A visual
track does not necessarily correspond to a single physical object or software
object.

The term "Web resource" is used in this document in
accordance with Web Characterization Terminology and Definitions Sheet [WEBCHAR] to
mean anything that can be identified by a Uniform Resource Identifier
(URI); refer to RFC 2396 [RFC2396].

For the latest version of any W3C specification please
consult the list of W3C Technical Reports at
http://www.w3.org/TR/. Some documents listed below may have been superseded
since the publication of this document.

Note: In this document, bracketed labels such as "[HTML4]"
link to the corresponding entries in this section. These labels are also
identified as references through markup.

There are two recommended ways to refer to the "User Agent Accessibility
Guidelines 1.0" (and to W3C documents in general):

References to a specific version of "User Agent Accessibility Guidelines
1.0". For example, use the "this version" URI to refer to
the current document: http://www.w3.org/TR/2002/WD-UAAG10-20020821/.

References to the latest version of "User Agent Accessibility Guidelines
1.0". Use the "latest version" URI to refer to the most recently published
document in the series: http://www.w3.org/TR/UAAG10/.

In almost all cases, references (either by name or by link) should be to a
specific version of the document. W3C will make every effort to make this
document indefinitely available at its original address in its original form.
The top of this document includes the relevant catalog metadata for specific
references (including title, publication date, "this version"
URI, editors' names, and copyright information).

An XHTML 1.0
[XHTML10] paragraph including a reference to this specific document
might be written:

For very general references to this document (where stability of content,
anchors, etc., is not required), it may be appropriate to refer to the latest
version of this document. In this case, please use the "latest version" URI at
the top of this document.

"Web
Characterization Terminology and Definitions Sheet", B. Lavoie, H.
F. Nielsen, eds., 24 May 1999. This is a W3C Working Draft that defines some
terms to establish a common understanding about key Web concepts. This W3C
Working Draft is http://www.w3.org/1999/05/WCA-terms/01.